1.What is the difference between user controls and custom controls?
CUSTOM CONTROLS are DLL'S.It can be placed in the toolbox.Drag and drop controls.
USER CONTROLS: are pages (.ascx).It can not be placed in the tool box.
2.what are the 3 types of session state modes?
a. Inproc-session kept as live object in the web server(aspnet_wp.exe)
b. Stateserver-Session serialized and stored in memory in a separate process(aspnet_state.exe),we can use for webform architecture.
c. SQLServer-Session serialized and stored in sql server.
3. what are the 6 types of validation controls in ASP.NET?
1.Required Field validator.2.Range validator.3.Regular Expression validator.4.compare validator.5.custom validator. 6.validation summary.
4.What are the 3 types of caching in ASP.NET?
1. Output Caching(Page Caching)- stores the responses from an asp.net page(aspx) or user control(.ascx).
2. Fragment Caching(Partial Caching)- Only stores the portion of a page.
3. Data Caching is the programmatic way to your objects to a managed cache.
//Add item
Cache["TopProducts"] = objTopProductsDataset;
//Retrieve item
objDataset = Cache["TopProducts"];
.5.How to Manage state in ASP.NET?
we can manage the state in two ways
Clent based techniques are Viewstate, Query strings and Cookies.
Server based techniques are Application and Session
6.What is the difference between overloading and shadowing?
Overloading: A Member has the name, but something else in the signature is different.
Shadowing: A member shadows another member if the derived member replaces the base member
7. what is the difference between overloading and overriding?
Overloading: Method name remains the same with different signatures.
Overriding: Method name and Signatures must be the same.
8. what is the difference between Manifest and Metadata?
Manifest: Manifest describes assembly itself.
Assembly Name, version number, culture, strongname, listof all all files, Type references and referenced assemblies.
Metadata: Metadata describes contents in an assembly
classes, interfaces, enums, structs, etc., and their containing namespaces, the name of each type, its visibility/scope, its base class, the interfaces it implemented, its methods and their scope, and each method’s parameters, type’s properties, and so on.
9.What is Boxing and Unboxing?
Boxing is an implicit conversion of a value type to the type object
int i = 123; // A value type
Object box = i // Boxing
CASTING : casting is the process of converting a variable from one type to another (from a string to an integer )
Unboxing is an explicit conversion from the type object to a value type
int i = 123; // A value type
object box = i; // Boxing
int j = (int)box; // Unboxing
10.what are the method parameter in c#?
C# is having 4 parameter types which are
1.Value Parameter. default parameter type. Only Input
2.Reference(ref) Parameter. Input\Output
3.Output(out) Parameter.
4.Parameter(params) Arrays
11.what are value types and reference types?
Value type
bool, byte,chat, decimal,double,enum , float, int, long, sbyte, short, strut, uint, ulong, ushort
Value types are stored in the Stack
Reference type
class, delegate, interface, object, string
Reference types are stored in the Heap
12.what are the two activation modes for .NET Remoting?
1. Singleton 2. Singlecall
13.what's singlecall Activation mode used for ?
The Server Object is instantiated for responding to just one single request
14.what's the singleton Activation mode used for?
The server object is instantiated for responding number of clients
15.what are the channels and Formatters?
Channels
HTTP and TCP
Binay Over TCP is most efficient
SOAP over HTTP is most interoperable
Formatters
Binary and SOAP
16.What are the two Authentication modes for SQL server connection?
1. Trusted Connection - Windows Authentication
2. Non trusted Connection - Sql Server Authentication(its preferable for webservices)
17.What is typed dataset?
Data Access is normally done using indexes on collections in object model.
In ADO.NET it is possible to create a variation on a Dataset that does support
such syntax. Such Dataset is called "Typed Dataset".
Errors in the syntax are detected during compile time rather than runtime.
Advantages of Typed Dataset:
1.The data designer tool generates typed Datasets.
2. When we type the name of a dataset while writing a code,
weget a list of all available tables in the dataset.No need to emember the table names.
For (eg) instead of typing
myDataset.Tables("products")
we can type myDataset.products.
18.what is DataReader?
DataReader is a read only stream of data returned from
the database as the query executes.
It contains one row of data in memory at a time and is
restricted to navigating forward only in the results one record at a time.
Datareader supports access to multiple result sets but only one at a time and in the order retrieved.
In
which means a Datareader requires a connection to the Database throughout its usage.
o/p parameters or return values are only available thrugh the Datareader once the connection is closed.
19.Difference between Dataset and Recordset?
The Recordset was not XML-based and could not be serialized to XML easily or flexibly.
Finally, a Recordset was not independent of a data store because it tracked a Connection object
and through its methods could send queries to the data source to populate, update,
and refresh its data.
To that end, the Recordset contained functionality found in the ADO.NET DataSet,
data reader, and data adapter objects.
Similar to the DataSet, a Recordset could be disconnected from its data store
and therefore act as an in-memory cache of data.
Of course, it could also be used in a connected model depending on the cursor options that were set.
Although the Recordset object stored multiple versions of each column for each of its rows,
it was not by nature able to represent multiple tables without the use of the Data Shape Provider.
.
21.What isan Assembly, Private Assembly and SharedAssembly,Strong Name?
Assembly: Assemblies are basically the compiled code in .Net which contains the code in Microsoft Intermediate Langauge and one more thing that assembiles do for us as compared to dlls is they can maintain versioning with the help of the manifest.
You dont need to register the assemblies after compiling like we needed in dlls. you can put the assemblies in the bin folder and refer the namespaces from there.
In short find the assembly description as :
Assemblies are the building blocks of .NET Framework applications; they form the fundamental unit of deployment, version control, reuse, activation scoping, and security permissions. An assembly is a collection of types and resources that are built to work together and form a logical unit of functionality. An assembly provides the common language runtime with the information it needs to be aware of type implementations. To the runtime, a type does not exist outside the context of an assembly.
Private assembly is used inside an application only and does not have to be identified by a strong name
Shared assembly can be used by multiple applications and has to have a strong name.
Strong Name : A strong name includes the name of the assembly, version number, culture identity, and a public key token.
22.what is an Delegate?
A strongly typed function pointer. A delegate object encapsulates a reference to a method.
23.what are webservices?
A Web Service is an application that delivers a service across the Internet using the standards and technologies defined in the Web Services architecture in a platform-independent and language-neutral fashion.
Web Services rely on several XML protocols based on open standards that are collectively known as the Web Services architecture
24.Define Automatic memory Management:
c# Provides Automatic memory Management.
Automatic memory Management increases code quality and enhances developer productivity without negatively impacting either expressiveness or performance. Developers are freed from this burdensome task.
25.Define Threading:
It's a process of creating applications that can perform multiple tasks independently.
26Difference Between XML AND HTML?
XML:
User definable tags.
Content driven
End tags required for well formed documents
Quotes required around attributes values
Slash required in empty tags
HTML :
Defined set of tags designed for web display
Format driven
End tags not required
Quotes not required
Slash not required
27.What is XSLTand what is it's use?
XSL Transformations (XSLT) is yet another popular W3C specification that defines XML-based syntax, used to transform XML documents to any other text format, such as HTML, text, XML, etc. XSLT stylesheets can be applied on the source XML document to transform XML into some other XML, or text, HTML, or any other text format.
28.What is Diffgram?
It's an XML format.
It'sone of the two xml formats that uses to render Dataset object contents to XML.
For reading database data to an XML file to be sent to a webservice.
29.what is the Role of XSL?
Querying a database and then formatting the result set so that it can be validated as an XML document allows developers to translate the data into an HTML table using XSLT rules. Consequently, the format of the resulting HTML table can be modified without changing the database query or application code since the document rendering logic is isolated to the XSLT rules
30.What is SAX?
Simple API for XML Processing (SAX) is an alternative to DOM, and can be used to parse XML documents. SAX is based on streaming model. The SAX parser reads input XML stream and generates various parsing events that an application can handle. With each parsing event, the parser sends sufficient information about the node being parsed. Unlike DOM, SAX does not build an in-memory representation of the source XML document, and hence it is an excellent alternative when parsing large XML documents, as SAX does not require that much memory (and resources). Unlike DOM, SAX is not defined/controlled by W3C. See http://www.saxproject.org/ for details.
32.Give a few examples of types of applications that can benefit from using XML.
XML allows content management systems to store documents independently of their format, which thereby reduces data redundancy. Another answer relates to B2B exchanges or supply chain management systems. In these instances, XML provides a mechanism for multiple companies to exchange data according to an agreed upon set of rules. A third common response involves wireless applications that require WML to render data on hand held devices.
33.When constructing an XML DTD, how do you create an external entity reference in an attribute value?
when using SGML, XML DTDs don't support defining external entity references in attribute values.
34.Give some examples of XML DTDs or schemas that you have worked with.
Although XML does not require data to be validated against a DTD, many of the benefits of using the technology are derived from being able to validate XML documents against business or technical architecture rules. Polling for the list of DTDs that developers have worked with provides insight to their general exposure to the technology.commonly used DTDs such as FpML, DocBook, HRML, and RDF, as well as experience designing a custom DTD for a particular project
35.What is SOAP and how does it relate to XML?
The Simple Object Access Protocol (SOAP) uses XML to define a protocol for the exchange of information in distributed computing environments. SOAP consists of three components: an envelope, a set of encoding rules, and a convention for representing remote procedure calls. Unless experience with SOAP is a direct requirement for the open position, knowing the specifics of the protocol, or how it can be used in conjunction with HTTP, is not as important as identifying it as a natural application of XML.
36.What is WSDL?
Another key standard in the Web Services architecture is the Web Services Description Language, or WSDL for short. Whereas SOAP is responsible for providing a platform-neutral protocol for transporting data types and interapplication messaging, WSDL is an XML grammar responsible for exposing the methods, arguments, and return parameters exposed by a particular Web Service.
37.What’s the difference between authentication and authorization?
Authentication happens first. You verify user’s identity based on credentials. Authorization is making sure the user only gets access to the resources he has credentials for.
38.Explain loosely coupled events.
Loosely coupled events enable an object (publisher) to publish an event. Other objects (subscribers) can subscribe to an event. COM+ does not require publishers or subscribers to know about each other. Therefore, loosely coupled events greatly simplify the programming model for distributed applications.
39.Define scalability.
The application meets its requirement for efficiency even if the number of users increases.
40.Define reliability.
The application generates correct and consistent information all the time.
41.Define availability.
Users can depend on using the application when needed.
42.Define security.
The application is never disrupted or compromised by the efforts of malicious or ignorant users
43.Define manageability.
Deployment and maintenance of the application is as efficient and painless as possible
44.Explain durability.
Make sure that the system can return to its original state in case of a failure.
45.Explain integrity.
Ensure data integrity by protecting concurrent transactions from seeing or being adversely affected by each other’s partial and uncommitted results.
46.Explain consistency.
We must ensure that the system is always left at the correct state in case of the failure or success of a transaction.
47.Explain JIT activation.
The objective of JIT activation is to minimize the amount of time for which an object lives and consumes resources on the server. With JIT activation, the client can hold a reference to an object on the server for a long time, but the server creates the object only when the client calls a method on the object. After the method call is completed, the object is freed and its memory is reclaimed. JIT activation enables applications to scale up as the number of users increases
48.Define Constructors and destructors
The create and destroy methods - often called constructors and destructors - are usually implemented for any abstract data type. Occasionally, the data type's use or semantics are such that there is only ever one object of that type in a program. In that case, it is possible to hide even the object's `handle' from the user. However, even in these cases, constructor and destructor methods are often provided.
Of course, specific applications may call for additional methods, e.g. we may need to join two collections (form a union in set terminology) - or may not need all of these.
How big is the datatype int in .NET? 32 bits.
How big is the char? 16 bits (Unicode).
How do you initiate a string without escaping each backslash?
Put an @ sign in front of the double-quoted string.
What are valid signatures for the Main function?
public static void Main()
public static int Main()
public static void Main( string[] args )
public static int Main(string[] args )
Does Main() always have to be public? No.
How do you initialize a two-dimensional array that you don’t know the dimensions of?
int [, ] myArray; //declaration
myArray= new int [5, 8]; //actual initialization
What’s the access level of the visibility type internal? Current assembly.
What’s the difference between struct and class in C#?
Structs cannot be inherited.
Structs are passed by value, not by reference.
Struct is stored on the stack, not the heap.
Explain encapsulation. The implementation is hidden, the interface is exposed.
What data type should you use if you want an 8-bit value that’s signed? sbyte.
Speaking of Boolean data types, what’s different between C# and C/C++? There’s no conversion between 0 and false, as well as any other number and true, like in C/C++.
Where are the value-type variables allocated in the computer RAM? Stack.
Where do the reference-type variables go in the RAM?
The references go on the stack, while the objects themselves go on the heap. However, in reality things are more elaborate.
What is the difference between the value-type variables and reference-type variables in terms of garbage collection?
The value-type variables are not garbage-collected, they just fall off the stack when they fall out of scope, the reference-type objects are picked up by GC when their references go null.
How do you convert a string into an integer in .NET?
Int32.Parse(string), Convert.ToInt32()
How do you box a primitive data type variable?
Initialize an object with its value, pass an object, cast it to an object
Why do you need to box a primitive variable?
To pass it by reference or apply a method that an object supports, but primitive doesn’t.
What’s the difference between Java and .NET garbage collectors?
Sun left the implementation of a specific garbage collector up to the JRE developer, so their performance varies widely, depending on whose JRE you’re using. Microsoft standardized on their garbage collection.
How do you enforce garbage collection in .NET?
System.GC.Collect();
Can you declare a C++ type destructor in C# like ~MyClass()? Yes, but what’s the point, since it will call Finalize(), and Finalize() has no guarantees when the memory will be cleaned up, plus, it introduces additional load on the garbage collector. The only time the finalizer should be implemented, is when you’re dealing with unmanaged code.
What’s different about namespace declaration when comparing that to package declaration in Java?
No semicolon. Package declarations also have to be the first thing within the file, can’t be nested, and affect all classes within the file.
What’s the difference between const and readonly?
You can initialize readonly variables to some runtime values. Let’s say your program uses current date and time as one of the values that won’t change. This way you declare
public readonly string DateT = new DateTime().ToString().
Can you create enumerated data types in C#? Yes.
What’s different about switch statements in C# as compared to C++?
No fall-throughs allowed.
What happens when you encounter a continue statement inside the for loop?
The code for the rest of the loop is ignored, the control is transferred back to the beginning of the loop.
Is goto statement supported in C#? How about Java?
Gotos are supported in C#to the fullest. In Java goto is a reserved keyword that provides absolutely no functionality.
Describe the compilation process for .NET code?
Source code is compiled and run in the .NET Framework using a two-stage process. First, source code is compiled to Microsoft intermediate language (MSIL) code using a .NET Framework-compatible compiler, such as that for Visual Basic .NET or Visual C#.
Second, MSIL code is compiled to native code.
Name any 2 of the 4 .NET authentification methods. ASP.NET, in conjunction with Microsoft Internet Information Services (IIS), can authenticate user credentials such as names and passwords using any of the following authentication methods:
Windows: Basic, digest, or Integrated Windows Authentication (NTLM or Kerberos).
Microsoft Passport authentication
Forms authentication
Client Certificate authentication
How do you turn off SessionState in the web.config file?
In the system.web section of web.config, you should locate the httpmodule tag and you simply disable session by doing a remove tag with attribute name set to session.
CodeBehind is relevant to Visual Studio.NET only.
What’s a bubbled event?
When you have a complex control, likeDataGrid, writing an event processing routine for each object (cell, button,row, etc.) is quite tedious. The controls can bubble up their eventhandlers, allowing the main DataGrid event handler to take care of itsconstituents.
Suppose you want a certain ASP.NET function executed on MouseOver overa
certain button.
Where do you add an event handler?
It’s the Attributesproperty, the Add function inside that property. So btnSubmit.Attributes.Add("onMouseOver","someClientCode();")
A simple"Javascript:ClientCode();” in the button control of the .aspx
page will attach the handler (javascript function)to the onmouseover event.
What data type does the RangeValidator control support?
Integer, String and Date.
Where would you use an iHTTPModule, and what are the limitations of any
approach you might take in implementing one?
One of ASP.NET’s most useful features is the extensibility
of the HTTP pipeline, the path that data takes between client and server.
You can use them to extend your ASP.NET applications by adding pre- and post-processing
to each HTTP request coming into your application. For example, if you wanted
custom authentication facilities for your application, the best technique
would be to intercept the request when it comes in and process the request
in a custom HTTP module.
Explain what a diffgram is, and a good use for one?
A DiffGram is an XML format that is used to identify current and original versions of data
elements. The DataSet uses the DiffGram format to load and persist its contents,
and to serialize its contents for transport across a network connection. When
a DataSet is written as a DiffGram, it populates the DiffGram with all the
necessary information to accurately recreate the contents, though not the
schema, of the DataSet, including column values from both the Original and
Current row versions, row error information, and row order.
Interview Questions
ASP.NET
1. Describe the role of inetinfo.exe, aspnet_isapi.dll andaspnet_wp.exe in the page loading process. inetinfo.exe is theMicrosoft IIS server running, handling ASP.NET requests among other things.When an ASP.NET request is received (usually a file with .aspx extension),the ISAPI filter aspnet_isapi.dll takes care of it by passing the request tothe actual worker process aspnet_wp.exe.
2. What’s the difference between Response.Write() andResponse.Output.Write()?
The latter one allows you to write formattedoutput.
3. What methods are fired during the page load? Init() - when the pageis instantiated, Load() - when the page is loaded into server memory,PreRender() - the brief moment before the page is displayed to the user asHTML, Unload() - when page finishes loading.
4. Where does the Web page belong in the .NET Framework class hierarchy?System.Web.UI.Page
5. Where do you store the information about the user’s locale? System.Web.UI.Page.Culture
6. What’s the difference between Codebehind="MyCode.aspx.cs" andSrc="MyCode.aspx.cs"? CodeBehind is relevant to Visual Studio.NET only.
7. What’s a bubbled event? When you have a complex control, like DataGrid, writing an event processing routine for each object (cell, button, row, etc.) is quite tedious. The controls can bubble up their eventhandlers, allowing the main DataGrid event handler to take care of its constituents.
8. Suppose you want a certain ASP.NET function executed on MouseOver overa certain button. Where do you add an event handler? It’s the Attributesproperty, the Add function inside that property. So btnSubmit.Attributes.Add("onMouseOver","someClientCode();")
9. What data type does the RangeValidator control support? Integer,String and Date.
10. Explain the differences between Server-side and Client-side code?
Server-side code runs on the server. Client-side code runs in the clients’ browser.
11. What type of code (server or client) is found in a Code-Behind class? Server-side code.
12. Should validation (did the user enter a real date) occur server-side or client-side? Why? Client-side. This reduces an additional request to the server to validate the users input.
13. What does the "EnableViewState" property do? Why would I want it on or off?
It enables the viewstate on the page. It allows the page to save the users input on a form.
14. What is the difference between Server.Transfer and Response.Redirect?
Why would I choose one over the other? Server.Transfer is used to post a form to another page. Response.Redirect is used to redirect the user to another page or site.
15. Can you explain the difference between an ADO.NET Dataset and an ADO Recordset?
· A DataSet can represent an entire relational database in memory, complete with tables, relations, and views.
· A DataSet is designed to work without any continuing connection to the original data source.
· Data in a DataSet is bulk-loaded, rather than being loaded on demand.
· There's no concept of cursor types in a DataSet.
· DataSets have no current record pointer You can use For Each loops to move through the data.
· You can store many edits in a DataSet, and write them to the original data source in a single operation.
· Though the DataSet is universal, other objects in ADO.NET come in different versions for different data sources.
16. Can you give an example of what might be best suited to place in the Application_Start and Session_Start subroutines? This is where you can set the specific variables for the Application and Session objects.
17. If I’m developing an application that must accommodate multiple security levels though secure login and my ASP.NET web application is spanned across three web-servers (using round-robin load balancing) what would be the best approach to maintain login-in state for the users? Maintain the login state security through a database.
18. Can you explain what inheritance is and an example of when you might use it?
When you want to inherit (use the functionality of) another class. Base Class Employee. A Manager class could be derived from the Employee base class.
19. Whats an assembly?
Assemblies are the building blocks of the .NET framework. Overview of assemblies from MSDN
20. Describe the difference between inline and code behind.
Inline code written along side the html in a page. Code-behind is code written in a separate file and referenced by the .aspx page.
21. Explain what a diffgram is, and a good use for one?
The DiffGram is one of the two XML formats that you can use to render DataSet object contents to XML. For reading database data to an XML file to be sent to a Web Service.
22. Whats MSIL, and why should my developers need an appreciation of it if at all? MSIL is the Microsoft Intermediate Language. All .NET compatible languages will get converted to MSIL.
23. Which method do you invoke on the DataAdapter control to load your generated dataset with data? The .Fill() method
24. Can you edit data in the Repeater control? No, it just reads the information from its data source
25. Which template must you provide, in order to display data in a Repeater control? ItemTemplate
26. How can you provide an alternating color scheme in a Repeater control? Use the AlternatingItemTemplate
27. What property must you set, and what method must you call in your code, in order to bind the data from some data source to the Repeater control? You must set the DataSource property and call the DataBind method.
28. What base class do all Web Forms inherit from? The Page class.
29. Name two properties common in every validation control? ControlToValidate property and Text property.
30. What tags do you need to add within the asp:datagrid tags to bind columns manually? Set AutoGenerateColumns Property to false on the datagrid tag
31. What tag do you use to add a hyperlink column to the DataGrid?
32. What is the transport protocol you use to call a Web service? SOAP is the preferred protocol.
33. True or False: A Web service can only be written in .NET? False
34. What does WSDL stand for? (Web Services Description Language)
35. Where on the Internet would you look for Web services? (http://www.uddi.org)
36. Which property on a Combo Box do you set with a column name, prior to setting the DataSource, to display data in the combo box? DataTextField property
37. Which control would you use if you needed to make sure the values in two different controls matched? CompareValidator Control
38. True or False: To test a Web service you must create a windows application or Web application to consume this service?
False, the webservice comes with a test page and it provides HTTP-GET method to test.
39. How many classes can a single .NET DLL contain? It can contain many classes.
Describe the role of inetinfo.exe, aspnet_isapi.dll andaspnet_wp.exe
in the page loading process. inetinfo.exe is theMicrosoft IIS server running,
handling ASP.NET requests among other things.When an ASP.NET request is received
(usually a file with .aspx extension),the ISAPI filter aspnet_isapi.dll takes
care of it by passing the request tothe actual worker process aspnet_wp.exe.
What’s the difference between Response.Write() andResponse.Output.Write()?
The latter one allows you to write formattedoutput.
What methods are fired during the page load? Init() –
when the page is instantiated, Load() - when the page is loaded into server memory,PreRender()
- the brief moment before the page is displayed to the user asHTML, Unload()
- when page finishes loading.
Where does the Web page belong in the .NET Framework class hierarchy? System.Web.UI.Page
Where do you store the information about the user’s locale? System.Web.UI.Page.Culture
What’s the difference between Codebehind="MyCode.aspx.cs" andSrc="MyCode.aspx.cs"?
CodeBehind is relevant to Visual Studio.NET only.
What’s a bubbled event? When you have a complex control, likeDataGrid,
writing an event processing routine for each object (cell, button,row, etc.)
is quite tedious. The controls can bubble up their eventhandlers, allowing
the main DataGrid event handler to take care of itsconstituents.
Suppose you want a certain ASP.NET function executed on MouseOver overa
certain button. Where do you add an event handler?
It’s the Attributesproperty, the Add function inside that property. So
btnSubmit.Attributes.Add("onMouseOver","someClientCode();")
A simple”Javascript:ClientCode();” in the button control of the .aspx
page will attach the handler (javascript function)to the onmouseover event.
What data type does the RangeValidator control support? Integer,String
and Date.
Where would you use an iHTTPModule, and what are the limitations of any
approach you might take in implementing one? One of ASP.NET’s most useful
features is the extensibility
of the HTTP pipeline, the path that data takes between client and server.
You can use them to extend your ASP.NET applications by adding pre- and post-processing
to each HTTP request coming into your application. For example, if you wanted
custom authentication facilities for your application, the best technique
would be to intercept the request when it comes in and process the request
in a custom HTTP module.
Explain what a diffgram is, and a good use for one? A DiffGram is
an XML format that is used to identify current and original versions of data
elements. The DataSet uses the DiffGram format to load and persist its contents,
and to serialize its contents for transport across a network connection. When
a DataSet is written as a DiffGram, it populates the DiffGram with all the
necessary information to accurately recreate the contents, though not the
schema, of the DataSet, including column values from both the Original and
Current row versions, row error information, and row order.
Explain the differences between Server-side and Client-side code?
What type of code (server or client) is found in a Code-Behind class?
Should validation (did the user enter a real date) occur server-side or client-side? Why?
What does the "EnableViewState" property do? Why would I want it on or off?
What is the difference between Server.Transfer and Response.Redirect? Why would I choose one over the other?
Can you give an example of when it would be appropriate to use a web service as opposed to a non-serviced .NET component?
Let's say I have an existing application written using Visual Studio (VB InterDev and this application utilizes Windows COM+ transaction services. How would you approach migrating this application to .NET?
Can you explain the difference between an ADO.NET Dataset and an ADO Recordset?
Can you give an example of what might be best suited to place in the Application_Start and Session_Start subroutines?
If I'm developing an application that must accomodate multiple security levels though secure login and my ASP.NET web appplication is spanned across three web-servers (using round-robbin load balancing) what would be the best approach to maintain login-in state for the users?
What are ASP.NET Web Forms? How is this technology different than what is available though ASP (?
How does VB.NET/C# achieve polymorphism?
Can you explain what inheritance is and an example of when you might use it?
How would you implement inheritance using VB.NET/C#?
Whats an assembly?
Describe the difference between inline and code behind - which is best in a loosely coupled solution?
Explain what a diffgram is, and a good use for one?
Where would you use an iHTTPModule, and what are the limitations of anyapproach you might take in implementing one?
What are the disadvantages of viewstate/what are the benefits?
Describe session handling in a webfarm, how does it work and what are the limits?
How would you get ASP.NET running in Apache web servers - why would you even do this?
Whats MSIL, and why should my developers need an appreciation of it if at all?
In what order do the events of an ASPX page execute. As a developer is it important to undertsand these events?
Which method do you invoke on the DataAdapter control to load your generated dataset with data?
Can you edit data in the Repeater control?
Which template must you provide, in order to display data in a Repeater control?
How can you provide an alternating color scheme in a Repeater control?
What property must you set, and what method must you call in your code, in order to bind the data from some data source to the Repeater control?
What base class do all Web Forms inherit from?
What method do you use to explicitly kill a user s session?
How do you turn off cookies for one page in your site?
Which two properties are on every validation control?
What tags do you need to add within the asp:datagrid tags to bind columns manually?
How do you create a permanent cookie?
What tag do you use to add a hyperlink column to the DataGrid?
What is the standard you use to wrap up a call to a Web service
Which method do you use to redirect the user to another page without performing a round trip to the client?
What is the transport protocol you use to call a Web service SOAP
True or False: A Web service can only be written in .NET
What does WSDL stand for?
What property do you have to set to tell the grid which page to go to when using the Pager object?
Where on the Internet would you look for Web services?
What tags do you need to add within the asp:datagrid tags to bind columns manually.
Which property on a Combo Box do you set with a column name, prior to setting the DataSource, to display data in the combo box?
How is a property designated as read-only?
Which control would you use if you needed to make sure the values in two different controls matched?
True or False: To test a Web service you must create a windows application or Web application to consume this service?
How many classes can a single .NET DLL contain?
Microsoft programming and databases :
3 main differences between flexgrid control and dbgrid control
ActiveX and Types of ActiveX Components in VB
Advantage of ActiveX Dll over Active Exe
Advantages of disconnected recordsets
Benefit of wrapping database calls into MTS transactions
Benefits of using MTS
Can database schema be changed with DAO, RDO or ADO?
Can you create a tabletype of recordset in Jet - connected ODBC database engine?
Constructors and destructors
Controls which do not have events
Default property of datacontrol
Define the scope of Public, Private, Friend procedures?
Describe Database Connection pooling relative to MTS
Describe: In of Process vs. Out of Process component. Which is faster?
Difference between a function and a subroutine, Dynaset and
Snapshot,early and late binding, image and picture controls,Linked Object and Embedded Object,listbox and combo box,Listindex and Tab index,modal and moduless window, Object and Class,Query unload and unload in form.
Declaration and Instantiation an object?
Draw and explain Sequence Modal of DAO
How can objects on different threads communicate with one another?
How can you force new objects to be created on new threads?
How does a DCOM component know where to instantiate itself?
How to register a component?
How to set a shortcut key for label?
Kind of components can be used as DCOM servers
Name of the control used to call a windows application
Name the four different cursor and locking types in
Need of zorder method, no of controls in form, Property used to add a menus at runtime, Property used to count number of items in a combobox,resize a label control according to your caption.
Return value of callback function, The need of tabindex property.
Thread pool and management of threads within a thread pool.
To set the command button for ESC, Which property needs to be changed?
Type Library and what is it's purpose?
Types of system controls, container objects, combo box
Under the ADO Command Object, what collection is responsible for input to stored procedures?
VB and Object Oriented Programming
What are the
NET Framework interview questions and interviewer's notes
.NET framework overview
Has own class libraries. System is the main namespace and all other namespaces are subsets of this.
It has CLR(Common language runtime, Common type system, common language specification)
All the types are part of CTS and Object is the base class for all the types.
If a language said to be .net complaint, it should be compatible with CTS and CLS.
All the code compiled into an intermediate language by the .Net language compiler, which is nothing but an assembly.
During runtime, JIT of CLR picks the IL code and converts into PE machine code and from there it processes the request.
CTS, CLS, CLR
Garbage Collection
Dispose, finalize, suppress finalize, Idispose interface
Assemblies, Namespace: Assembly is a collection of class/namespaces. An assembly contains Manifest, Metadata, Resource files, IL code
Com interoperability, adding references, web references
Database connectivity and providers
Application Domain
VB.Net
Class modifiers: public, private, friend, protected, protected friend, mustinherit, NotInheritable
Method modifiers: public, private
Overridable
Shadows
Overloadable
Overrides
Overloads
Set/Get Property
IIF
Inheritance
Polymorphism
Delegates
Events
Reflection
Boxing
UnBoxing
Casting
ASP.Net
Web Controls: Data grid (templates, sorting, paging, bound columns, unbound columns, data binding), Data list, repeater controls
HTML Controls
Code behind pages, system.web.ui.page base class
Web.config: App settings, identity (impersonate), authentication (windows, forms, anonymous, passport), authorization
Databind.eval
Trace, Debug
Output cache
Session management
Application, Session
Global.asax httpapplication
User controls, custom controls, custom rendered controls (postback event, postdatachanged event) usercontrol is the base class
Directives
ADO.Net
Command object (ExecuteNonquery, ExecuteReader, ExecuteXMLReader, ExecuteScalar)
DataAdapter object (Fill)
Dataset (collection of tables)
CommandBuiler object
Transaction Object
Isolation levels
1 What is the CLI? Is it the same as the CLR?
The CLI (Common Language Infrastructure) is the definiton of the fundamentals of the .NET framework - the Common Type System (CTS), metadata, the Virtual Execution Environment (VES) and its use of intermediate language (IL), and the support of multiple programming languages via the Common Language Specification (CLS). The CLI is documented through ECMA - see http://msdn.microsoft.com/net/ecma/ for more details.
The CLR (Common Language Runtime) is Microsoft's primary implementation of the CLI. Microsoft also have a shared source implementation known as ROTOR, for educational purposes, as well as the .NET Compact Framework for mobile devices. Non-Microsoft CLI implementations include Mono and DotGNU Portable.NET.
2.2 What is the CTS, and how does it relate to the CLS?
CTS = Common Type System. This is the full range of types that the .NET runtime understands. Not all .NET languages support all the types in the CTS.
2.3 What is IL?
2.4 What is C#?
C# is a new language designed by Microsoft to work with the .NET framework. In their "Introduction to C#" whitepaper, Microsoft describe C# as follows:
"C# is a simple, modern, object oriented, and type-safe programming language derived from C and C++. C# (pronounced “C sharp”) is firmly planted in the C and C++ family tree of languages, and will immediately be familiar to C and C++ programmers. C# aims to combine the high productivity of Visual Basic and the raw power of C++."
Substitute 'Java' for 'C#' in the quote above, and you'll see that the statement still works pretty well :-).
If you are a C++ programmer, you might like to check out my C# FAQ.
2.5 What does 'managed' mean in the .NET context?
The term 'managed' is the cause of much confusion. It is used in various places within .NET, meaning slightly different things.
Managed code: The .NET framework provides several core run-time services to the programs that run within it - for example exception handling and security. For these services to work, the code must provide a minimum level of information to the runtime. Such code is called managed code.
Managed data: This is data that is allocated and freed by the .NET runtime's garbage collector.
2.6 What is reflection?
All .NET compilers produce metadata about the types defined in the modules they produce. This metadata is packaged along with the module (modules in turn are packaged together in assemblies), and can be accessed by a mechanism called reflection. The System.Reflection namespace contains classes that can be used to interrogate the types for a module/assembly.
Using reflection to access .NET metadata is very similar to using ITypeLib/ITypeInfo to access type library data in COM, and it is used for similar purposes - e.g. determining data type sizes for marshaling data across context/process/machine boundaries.
3.1 What is an assembly?
An assembly is sometimes described as a logical .EXE or .DLL, and can be an application (with a main entry point) or a library. An assembly consists of one or more files (dlls, exes, html files etc), and represents a group of resources, type definitions, and implementations of those types. An assembly may also contain references to other assemblies. These resources, types and references are described in a block of data called a manifest. The manifest is part of the assembly, thus making the assembly self-describing.
An important aspect of assemblies is that they are part of the identity of a type. The identity of a type is the assembly that houses it combined with the type name. This means, for example, that if assembly A exports a type called T, and assembly B exports a type called T, the .NET runtime sees these as two completely different types. Furthermore, don't get confused between assemblies and namespaces - namespaces are merely a hierarchical way of organising type names. To the runtime, type names are type names, regardless of whether namespaces are used to organise the names. It's the assembly plus the typename (regardless of whether the type name belongs to a namespace) that uniquely indentifies a type to the runtime.
Assemblies are also important in .NET with respect to security - many of the security restrictions are enforced at the assembly boundary.
Finally, assemblies are the unit of versioning in .NET - more on this below.
3.2 How can I produce an assembly?
The simplest way to produce an assembly is directly from a .NET compiler. For example, the following C# program:
public class CTest
{
public CTest() { System.Console.WriteLine( "Hello from CTest" ); }
}
can be compiled into a library assembly (dll) like this:
csc /t:library ctest.cs
You can then view the contents of the assembly by running the "IL Disassembler" tool that comes with the .NET SDK.
3.3 What is the difference between a private assembly and a shared assembly?
Location and visibility: A private assembly is normally used by a single application, and is stored in the application's directory, or a sub-directory beneath. A shared assembly is normally stored in the global assembly cache, which is a repository of assemblies maintained by the .NET runtime. Shared assemblies are usually libraries of code which many applications will find useful, e.g. the .NET framework classes.
3.4 How do assemblies find each other?
3.5 How does assembly versioning work?
Each assembly has a version number called the compatibility version. Also each reference to an assembly (from another assembly) includes both the name and version of the referenced assembly.
The version number has four numeric parts (e.g. 5.5.2.33). Assemblies with either of the first two parts different are normally viewed as incompatible. If the first two parts are the same, but the third is different, the assemblies are deemed as 'maybe compatible'. If only the fourth part is different, the assemblies are deemed compatible. However, this is just the default guideline - it is the version policy that decides to what extent these rules are enforced. The version policy can be specified via the application configuration file.
Remember: versioning is only applied to shared assemblies, not private assemblies.
3.6 How can I develop an application that automatically updates itself from the web?
For .NET 1.x, use the Updater Application Block. For .NET 2.x, use ClickOnce.
4.1 What is an application domain?
An AppDomain can be thought of as a lightweight process. Multiple AppDomains can exist inside a Win32 process. The primary purpose of the AppDomain is to isolate applications from each other, and so it is particularly useful in hosting scenarios such as ASP.NET. An AppDomain can be destroyed by the host without affecting other AppDomains in the process.
Win32 processes provide isolation by having distinct memory address spaces. This is effective, but expensive. The .NET runtime enforces AppDomain isolation by keeping control over the use of memory - all memory in the AppDomain is managed by the .NET runtime, so the runtime can ensure that AppDomains do not access each other's memory.
One non-obvious use of AppDomains is for unloading types. Currently the only way to unload a .NET type is to destroy the AppDomain it is loaded into. This is particularly useful if you create and destroy types on-the-fly via reflection.
Microsoft have an AppDomain FAQ.
4.2 How does an AppDomain get created?
AppDomains are usually created by hosts. Examples of hosts are the Windows Shell, ASP.NET and IE. When you run a .NET application from the command-line, the host is the Shell. The Shell creates a new AppDomain for every application.
AppDomains can also be explicitly created by .NET applications. Here is a C# sample which creates an AppDomain, creates an instance of an object inside it, and then executes one of the object's methods:
using System.Runtime.Remoting;
using System.Reflection;
public class CAppDomainInfo : MarshalByRefObject
{
public string GetName() { return AppDomain.CurrentDomain.FriendlyName; }
}
public class App
{
public static int
{
AppDomain ad = AppDomain.CreateDomain( "Andy's new domain" );
CAppDomainInfo adInfo = (CAppDomainInfo)ad.CreateInstanceAndUnwrap(
Assembly.GetCallingAssembly().GetName().Name, "CAppDomainInfo" );
Console.WriteLine( "Created AppDomain name = " + adInfo.GetName() );
return 0;
}
}
4.3 Can I write my own .NET host?
Yes. For an example of how to do this, take a look at the source for the dm.net moniker developed by Jason Whittington and Don Box. There is also a code sample in the .NET SDK called CorHost.
5.1 What is garbage collection?
5.2 Is it true that objects don't always get destroyed immediately when the last reference goes away?
Yes. The garbage collector offers no guarantees about the time when an object will be destroyed and its memory reclaimed.
There was an interesting thread on the DOTNET list, started by Chris Sells, about the implications of non-deterministic destruction of objects in C#. In October 2000, Microsoft's Brian Harry posted a lengthy analysis of the problem. Chris Sells' response to Brian's posting is here.
5.3 Why doesn't the .NET runtime offer deterministic destruction?
Because of the garbage collection algorithm. The .NET garbage collector works by periodically running through a list of all the objects that are currently being referenced by an application. All the objects that it doesn't find during this search are ready to be destroyed and the memory reclaimed. The implication of this algorithm is that the runtime doesn't get notified immediately when the final reference on an object goes away - it only finds out during the next 'sweep' of the heap.
5.4 Is the lack of deterministic destruction in .NET a problem?
5.5 Should I implement Finalize on my class? Should I implement IDisposable?
This issue is a little more complex than it first appears. There are really two categories of class that require deterministic destruction - the first category manipulate unmanaged types directly (generally via an IntPtr representing an OS handle), whereas the second category manipulate managed types that require deterministic destruction. An example of the first category is a class with an IntPtr member representing an OS file handle. An example of the second category is a class with a System.IO.FileStream member.
For the first category, it makes sense to implement IDisposable and override Finalize. This allows the object user to 'do the right thing' by calling Dispose, but also provides a fallback of freeing the unmanaged resource in the Finalizer, should the calling code fail in its duty. However this logic does not apply to the second category of class, with only managed resources. In this case implementing Finalize is pointless, as managed member objects cannot be accessed in the Finalizer. This is because there is no guarantee about the ordering of Finalizer execution. So only the Dispose method should be implemented. (If you think about it, it doesn't really make sense to call Dispose on member objects from a Finalizer anyway, as the member object's Finalizer will do the required cleanup anyway.)
For classes that need to implement IDisposable and override Finalize, see Microsoft's documented pattern.
Note that some developers argue that implementing a Finalizer is always a bad idea, as it hides a bug in your code (i.e. the lack of a Dispose call). A less radical approach is to implement Finalize but include a Debug.Assert at the start, thus signalling the problem in developer builds but allowing the cleanup to occur in release builds.
5.6 Do I have any control over the garbage collection algorithm?
A little. For example the System.GC class exposes a Collect method, which forces the garbage collector to collect all unreferenced objects immediately.
5.7 How can I find out what the garbage collector is doing?
5.8 What is the lapsed listener problem?
The lapsed listener problem is one of the primary causes of leaks in .NET applications. It occurs when a subscriber (or 'listener') signs up for a publisher's event, but fails to unsubscribe. The failure to unsubscribe means that the publisher maintains a reference to the subscriber as long as the publisher is alive. For some publishers, this may be the duration of the application.
This situation causes two problems. The obvious problem is the leakage of the subscriber object. The other problem is the performance degredation due to the publisher sending redundant notifications to 'zombie' subscribers.
There are at least a couple of solutions to the problem. The simplest is to make sure the subscriber is unsubscribed from the publisher, typically by adding an Unsubscribe() method to the subscriber. Another solution, documented here by Shawn Van Ness, is to change the publisher to use weak references in its subscriber list.
5.9 When do I need to use GC.KeepAlive?
It's very unintuitive, but the runtime can decide that an object is garbage much sooner than you expect. More specifically, an object can become garbage while a method is executing on the object, which is contrary to most developers' expectations. Chris Brumme explains the issue on his blog. I've taken Chris's code and expanded it into a full app that you can play with if you want to prove to yourself that this is a real problem:
using System;
using System.Runtime.InteropServices;
class Win32
{
[DllImport("kernel32.dll")]
public static extern IntPtr CreateEvent( IntPtr lpEventAttributes,
bool bManualReset,bool bInitialState, string lpName);
[DllImport("kernel32.dll", SetLastError=true)]
public static extern bool CloseHandle(IntPtr hObject);
[DllImport("kernel32.dll")]
public static extern bool SetEvent(IntPtr hEvent);
}
class EventUser
{
public EventUser()
{
hEvent = Win32.CreateEvent( IntPtr.Zero, false, false, null );
}
~EventUser()
{
Win32.CloseHandle( hEvent );
Console.WriteLine("EventUser finalized");
}
public void UseEvent()
{
UseEventInStatic( this.hEvent );
}
static void UseEventInStatic( IntPtr hEvent )
{
//GC.Collect();
bool bSuccess = Win32.SetEvent( hEvent );
Console.WriteLine( "SetEvent " + (bSuccess ? "succeeded" : "FAILED!") );
}
IntPtr hEvent;
}
class App
{
static void
{
EventUser eventUser = new EventUser();
eventUser.UseEvent();
}
}
If you run this code, it'll probably work fine, and you'll get the following output:
SetEvent succeeded
EventDemo finalized
However, if you uncomment the GC.Collect() call in the UseEventInStatic() method, you'll get this output:
EventDemo finalized
SetEvent FAILED!
(Note that you need to use a release build to reproduce this problem.)
So what's happening here? Well, at the point where UseEvent() calls UseEventInStatic(), a copy is taken of the hEvent field, and there are no further references to the EventUser object anywhere in the code. So as far as the runtime is concerned, the EventUser object is garbage and can be collected. Normally of course the collection won't happen immediately, so you'll get away with it, but sooner or later a collection will occur at the wrong time, and your app will fail.
A solution to this problem is to add a call to GC.KeepAlive(this) to the end of the UseEvent method, as Chris explains.
6.1 What is serialization?
6.2 Does the .NET Framework have in-built support for serialization?
6.3 I want to serialize instances of my class. Should I use XmlSerializer, SoapFormatter or BinaryFormatter?
It depends. XmlSerializer has severe limitations such as the requirement that the target class has a parameterless constructor, and only public read/write properties and fields can be serialized. However, on the plus side, XmlSerializer has good support for customising the XML document that is produced or consumed. XmlSerializer's features mean that it is most suitable for cross-platform work, or for constructing objects from existing XML documents.
SoapFormatter and BinaryFormatter have fewer limitations than XmlSerializer. They can serialize private fields, for example. However they both require that the target class be marked with the [Serializable] attribute, so like XmlSerializer the class needs to be written with serialization in mind. Also there are some quirks to watch out for - for example on deserialization the constructor of the new object is not invoked.
6.4 Can I customise the serialization process?
Yes. XmlSerializer supports a range of attributes that can be used to configure serialization for a particular class. For example, a field or property can be marked with the [XmlIgnore] attribute to exclude it from serialization. Another example is the [XmlElement] attribute, which can be used to specify the XML element name to be used for a particular property or field.
6.5 Why is XmlSerializer so slow?
6.6 Why do I get errors when I try to serialize a Hashtable?
6.7 XmlSerializer is throwing a generic "There was an error reflecting MyClass" error. How do I find out what the problem is?
6.8 Why am I getting an InvalidOperationException when I serialize an ArrayList?
XmlSerializer needs to know in advance what type of objects it will find in an ArrayList. To specify the type, use the XmlArrayItem attibute like this:
{
public string Name;
public int Age;
}
public class Population
{
[XmlArrayItem(typeof(Person))] public ArrayList People;
}
7.1 What are attributes?
There are at least two types of .NET attribute. The first type I will refer to as a metadata attribute - it allows some data to be attached to a class or method. This data becomes part of the metadata for the class, and (like other class metadata) can be accessed via reflection. An example of a metadata attribute is [serializable], which can be attached to a class and means that instances of the class can be serialized.
[serializable] public class CTest {}
7.2 Can I create my own metadata attributes?
Yes. Simply derive a class from System.Attribute and mark it with the AttributeUsage attribute. For example:
[AttributeUsage(AttributeTargets.Class)]
public class InspiredByAttribute : System.Attribute
{
public string InspiredBy;
public InspiredByAttribute( string inspiredBy )
{
InspiredBy = inspiredBy;
}
}
[InspiredBy("Andy Mc's brilliant .NET FAQ")]
class CTest
{
}
class CApp
{
public static void
{
object[] atts = typeof(CTest).GetCustomAttributes(true);
foreach( object att in atts )
if( att is InspiredByAttribute )
Console.WriteLine( "Class CTest was inspired by {0}", ((InspiredByAttribute)att).InspiredBy );
}
}
7.3 Can I create my own context attibutes?
Yes. Take a look at Peter Drayton's Tracehook.NET.
8.1 What is Code Access Security (CAS)?
8.2 How does CAS work?
The CAS security policy revolves around two key concepts - code groups and permissions. Each .NET assembly is a member of a particular code group, and each code group is granted the permissions specified in a named permission set.
8.3 Who defines the CAS code groups?
Microsoft defines some default ones, but you can modify these and even create your own. To see the code groups defined on your system, run 'caspol -lg' from the command-line. On my system it looks like this:
Level = Machine
Code Groups:
1. All code: Nothing
1.1. Zone - MyComputer: FullTrust
1.1.1. Honor SkipVerification requests: SkipVerification
1.2. Zone - Intranet: LocalIntranet
1.3. Zone - Internet: Internet
1.4. Zone - Untrusted: Nothing
1.5. Zone - Trusted: Internet
1.6. StrongName -
0024000004800000940000000602000000240000525341310004000003
000000CFCB3291AA715FE99D40D49040336F9056D7886FED46775BC7BB5430BA4444FEF8348EBD06
F962F39776AE4DC3B7B04A7FE6F49F25F740423EBF2C0B89698D8D08AC48D69CED0FC8F83B465E08
07AC11EC1DCC7D054E807A43336DDE408A5393A48556123272CEEEE72F1660B71927D38561AABF5C
AC1DF1734633C602F8F2D5: Everything
8.4 How do I define my own code group?
Use caspol. For example, suppose you trust code from www.mydomain.com and you want it have full access to your system, but you want to keep the default restrictions for all other internet sites. To achieve this, you would add a new code group as a sub-group of the 'Zone - Internet' group, like this:
caspol -ag 1.3 -site www.mydomain.com FullTrust
Now if you run caspol -lg you will see that the new group has been added as group 1.3.1:
...
1.3. Zone - Internet: Internet
1.3.1. Site - www.mydomain.com: FullTrust
...
8.5 How do I change the permission set for a code group?
Use caspol. If you are the machine administrator, you can operate at the 'machine' level - which means not only that the changes you make become the default for the machine, but also that users cannot change the permissions to be more permissive. If you are a normal (non-admin) user you can still modify the permissions, but only to make them more restrictive. For example, to allow intranet code to do what it likes you might do this:
caspol -cg 1.2 FullTrust
8.6 Can I create my own permission set?
Yes. Use caspol -ap, specifying an XML file containing the permissions in the permission set. To save you some time, here is a sample file corresponding to the 'Everything' permission set - just edit to suit your needs. When you have edited the sample, add it to the range of available permission sets like this:
caspol -ap samplepermset.xml
Then, to apply the permission set to a code group, do something like this:
caspol -cg 1.3 SamplePermSet
(By default, 1.3 is the 'Internet' code group)
8.7 I'm having some trouble with CAS. How can I troubleshoot the problem?
8.8 I can't be bothered with CAS. Can I turn it off?
Yes, as long as you are an administrator. Just run:
9.1 Can I look at the IL for an assembly?
Yes. MS supply a tool called Ildasm that can be used to view the metadata and IL for an assembly.
9.2 Can source code be reverse-engineered from IL?
Yes, it is often relatively straightforward to regenerate high-level source from IL. Lutz Roeder's Reflector does a very good job of turning IL into C# or VB.NET.
9.3 How can I stop my code being reverse-engineered from IL?
You can buy an IL obfuscation tool. These tools work by 'optimising' the IL in such a way that reverse-engineering becomes much more difficult.
9.4 Can I write IL programs directly?
Yes. Peter Drayton posted this simple example to the DOTNET mailing list:
.assembly MyAssembly {}
.class MyApp {
.method static void
.entrypoint
ldstr "Hello, IL!"
call void System.Console::WriteLine(class System.Object)
ret
}
}
Just put this into a file called hello.il, and then run ilasm hello.il. An exe assembly will be generated.
9.5 Can I do things in IL that I can't do in C#?
10.1 Does .NET replace COM?
http://discuss.develop.com/archives/wa.exe?A2=ind0007&L=DOTNET&D=0&P=68241
http://discuss.develop.com/archives/wa.exe?A2=ind0007&L=DOTNET&P=R60761
The bottom line is that .NET has its own mechanisms for type interaction, and they don't use COM. No IUnknown, no IDL, no typelibs, no registry-based activation. This is mostly good, as a lot of COM was ugly. Generally speaking, .NET allows you to package and use components in a similar way to COM, but makes the whole thing a bit easier.
10.2 Is DCOM dead?
Pretty much, for .NET developers. The .NET Framework has a new remoting model which is not based on DCOM. DCOM was pretty much dead anyway, once firewalls became widespread and Microsoft got SOAP fever. Of course DCOM will still be used in interop scenarios.
10.3 Is COM+ dead?
Not immediately. The approach for .NET 1.0 was to provide access to the existing COM+ services (through an interop layer) rather than replace the services with native .NET ones. Various tools and attributes were provided to make this as painless as possible. Over time it is expected that interop will become more seamless - this may mean that some services become a core part of the CLR, and/or it may mean that some services will be rewritten as managed code which runs on top of the CLR.
http://discuss.develop.com/archives/wa.exe?A2=ind0007&L=DOTNET&P=R68370
10.4 Can I use COM components from .NET programs?
Yes. COM components are accessed from the .NET runtime via a Runtime Callable Wrapper (RCW). This wrapper turns the COM interfaces exposed by the COM component into .NET-compatible interfaces. For oleautomation interfaces, the RCW can be generated automatically from a type library. For non-oleautomation interfaces, it may be necessary to develop a custom RCW which manually maps the types exposed by the COM interface to .NET-compatible types.
Here's a simple example for those familiar with ATL. First, create an ATL component which implements the following IDL:
import "oaidl.idl";
import "ocidl.idl";
[
object,
uuid(EA013F93-487A-4403-86EC-FD9FEE5E6206),
helpstring("ICppName Interface"),
pointer_default(unique),
oleautomation
]
interface ICppName : IUnknown
{
[helpstring("method SetName")] HRESULT SetName([in] BSTR name);
[helpstring("method GetName")] HRESULT GetName([out,retval] BSTR *pName );
};
[
uuid(F5E4C61D-D93A-4295-A4B4-2453D4A4484D),
version(1.0),
helpstring("cppcomserver 1.0 Type Library")
]
library CPPCOMSERVERLib
{
importlib("stdole32.tlb");
importlib("stdole2.tlb");
[
uuid(600CE6D9-5ED7-4B4D-BB49-E8D5D5096F70),
helpstring("CppName Class")
]
coclass CppName
{
[default] interface ICppName;
};
};
When you've built the component, you should get a typelibrary. Run the TLBIMP utility on the typelibary, like this:
tlbimp cppcomserver.tlb
If successful, you will get a message like this:
Typelib imported successfully to CPPCOMSERVERLib.dll
You now need a .NET client - let's use C#. Create a .cs file containing the following code:
using System;
using CPPCOMSERVERLib;
public class MainApp
{
static public void
{
CppName cppname = new CppName();
cppname.SetName( "bob" );
Console.WriteLine( "Name is " + cppname.GetName() );
}
}
Compile the C# code like this:
csc /r:cppcomserverlib.dll csharpcomclient.cs
Note that the compiler is being told to reference the DLL we previously generated from the typelibrary using TLBIMP. You should now be able to run csharpcomclient.exe, and get the following output on the console:
10.5 Can I use .NET components from COM programs?
Yes. .NET components are accessed from COM via a COM Callable Wrapper (CCW). This is similar to a RCW (see previous question), but works in the opposite direction. Again, if the wrapper cannot be automatically generated by the .NET development tools, or if the automatic behaviour is not desirable, a custom CCW can be developed. Also, for COM to 'see' the .NET component, the .NET component must be registered in the registry.
Here's a simple example. Create a C# file called testcomserver.cs and put the following in it:
using System;
using System.Runtime.InteropServices;
namespace AndyMc
{
[ClassInterface(ClassInterfaceType.AutoDual)]
public class CSharpCOMServer
{
public CSharpCOMServer() {}
public void SetName( string name ) { m_name = name; }
public string GetName() { return m_name; }
private string m_name;
}
}
Then compile the .cs file as follows:
csc /target:library testcomserver.cs
You should get a dll, which you register like this:
regasm testcomserver.dll /tlb:testcomserver.tlb /codebase
Now you need to create a client to test your .NET COM component. VBScript will do - put the following in a file called comclient.vbs:
Dim dotNetObj
Set dotNetObj = CreateObject("AndyMc.CSharpCOMServer")
dotNetObj.SetName ("bob")
MsgBox "Name is " & dotNetObj.GetName()
and run the script like this:
wscript comclient.vbs
And hey presto you should get a message box displayed with the text "Name is bob".
An alternative to the approach above it to use the dm.net moniker developed by Jason Whittington and Don Box.
10.6 Is ATL redundant in the .NET world?
11.1 How does .NET remoting work?
.NET remoting involves sending messages along channels. Two of the standard channels are HTTP and TCP. TCP is intended for LANs only - HTTP can be used for LANs or WANs (internet).
Support is provided for multiple message serializarion formats. Examples are SOAP (XML-based) and binary. By default, the HTTP channel uses SOAP (via the .NET runtime Serialization SOAP Formatter), and the TCP channel uses binary (via the .NET runtime Serialization Binary Formatter). But either channel can use either serialization format.
There are a number of styles of remote access:
SingleCall. Each incoming request from a client is serviced by a new object. The object is thrown away when the request has finished.
Singleton. All incoming requests from clients are processed by a single server object.
Client-activated object. This is the old stateful (D)COM model whereby the client receives a reference to the remote object and holds that reference (thus keeping the remote object alive) until it is finished with it.
Distributed garbage collection of objects is managed by a system called 'leased based lifetime'. Each object has a lease time, and when that time expires the object is disconnected from the .NET runtime remoting infrastructure. Objects have a default renew time - the lease is renewed when a successful call is made from the client to the object. The client can also explicitly renew the lease.
If you're interested in using XML-RPC as an alternative to SOAP, take a look at Charles Cook's XML-RPC.Net.
11.2 How can I get at the Win32 API from a .NET program?
Use P/Invoke. This uses similar technology to COM Interop, but is used to access static DLL entry points instead of COM objects. Here is an example of C# calling the Win32 MessageBox function:
using System.Runtime.InteropServices;
class MainApp
{
[DllImport("user32.dll", EntryPoint="MessageBox", SetLastError=true, CharSet=CharSet.Auto)]
public static extern int MessageBox(int hWnd, String strMessage, String strCaption, uint uiType);
public static void
{
MessageBox( 0, "Hello, this is PInvoke in operation!", ".NET", 0 );
}
}
Pinvoke.net is a great resource for off-the-shelf P/Invoke signatures.
11.3 How do I write to the application configuration file at runtime?
You don't. See http://www.interact-sw.co.uk/iangblog/2004/11/25/savingconfig.
11.4 What is the difference between an event and a delegate?
An event is just a wrapper for a multicast delegate. Adding a public event to a class is almost the same as adding a public multicast delegate field. In both cases, subscriber objects can register for notifications, and in both cases the publisher object can send notifications to the subscribers. However, a public multicast delegate has the undesirable property that external objects can invoke the delegate, something we'd normally want to restrict to the publisher. Hence events - an event adds public methods to the containing class to add and remove receivers, but does not make the invocation mechanism public.
See this post by Julien Couvreur for more discussion.
11.5 What size is a .NET object?
Each instance of a reference type has two fields maintained by the runtime - a method table pointer and a sync block. These are 4 bytes each on a 32-bit system, making a total of 8 bytes per object overhead. Obviously the instance data for the type must be added to this to get the overall size of the object. So, for example, instances of the following class are 12 bytes each:
class MyInt
{
...
private int x;
}
However, note that with the current implementation of the CLR there seems to be a minimum object size of 12 bytes, even for classes with no data (e.g. System.Object).
Values types have no equivalent overhead.
What is .NET Framework?
The .NET Framework has two main components: the common language runtime and the .NET Framework class library.
You can think of the runtime as an agent that manages code at execution time, providing core services such as memory management, thread management, and remoting, while also enforcing strict type safety and other forms of code accuracy that ensure security and robustness.
The class library, is a comprehensive, object-oriented collection of reusable types that you can use to develop applications ranging from traditional command-line or graphical user interface (GUI) applications to applications based on the latest innovations provided by ASP.NET, such as Web Forms and XML Web services.
What is CLR, CTS, CLS?
The .NET Framework provides a runtime environment called the Common Language Runtime or CLR (similar to the Java Virtual Machine or JVM in Java), which handles the execution of code and provides useful services for the implementation of the program. CLR takes care of code management at program execution and provides various beneficial services such as memory management, thread management, security management, code verification, compilation, and other system services. The managed code that targets CLR benefits from useful features such as cross-language integration, cross-language exception handling, versioning, enhanced security, deployment support, and debugging.
Common Type System (CTS) describes how types are declared, used and managed in the runtime and facilitates cross-language integration, type safety, and high performance code execution.
The CLS is simply a specification that defines the rules to support language integration in such a way that programs written in any language, yet can interoperate with one another, taking full advantage of inheritance, polymorphism, exceptions, and other features. These rules and the specification are documented in the ECMA proposed standard document, "Partition I Architecture", http://msdn.microsoft.com/net/ecma/
What are the new features of Framework 1.1 ?
Native Support for Developing
Enable Execution of Windows Forms Assemblies Originating from the Internet
Assemblies originating from the Internet zone—for example, Microsoft Windows® Forms controls embedded in an Internet-based Web page or Windows Forms assemblies hosted on an Internet Web server and loaded either through the Web browser or programmatically using the System.Reflection.Assembly.LoadFrom() method—now receive sufficient permission to execute in a semi-trusted manner. Default security policy has been changed so that assemblies assigned by the common language runtime (CLR) to the Internet zone code group now receive the constrained permissions associated with the Internet permission set. In the .NET Framework 1.0 Service Pack 1 and Service Pack 2, such applications received the permissions associated with the Nothing permission set and could not execute.
Enable Code Access Security for ASP.NET Applications
Systems administrators can now use code access security to further lock down the permissions granted to ASP.NET Web applications and Web services. Although the operating system account under which an application runs imposes security restrictions on the application, the code access security system of the CLR can enforce additional restrictions on selected application resources based on policies specified by systems administrators. You can use this feature in a shared server environment (such as an Internet service provider (ISP) hosting multiple Web applications on one server) to isolate separate applications from one another, as well as with stand-alone servers where you want applications to run with the minimum necessary privileges.
Native Support for Communicating with ODBC and Oracle Databases
Unified Programming Model for Smart Client Application Development
The Microsoft .NET Compact Framework brings the CLR, Windows Forms controls, and other .NET Framework features to small devices. The .NET Compact Framework supports a large subset of the .NET Framework class library optimized for small devices.
Support for IPv6
The .NET Framework 1.1 supports the emerging update to the Internet Protocol, commonly referred to as IP version 6, or simply IPv6. This protocol is designed to significantly increase the address space used to identify communication endpoints in the Internet to accommodate its ongoing growth.
http://msdn.microsoft.com/netframework/technologyinfo/Overview/whatsnew.aspx
Is .NET a runtime service or a development platform?
Ans: It's both and actually a lot more. Microsoft .NET includes a new way of delivering software and services to businesses and consumers. A part of Microsoft.NET is the .NET Frameworks. The .NET frameworks SDK consists of two parts: the .NET common language runtime and the .NET class library. In addition, the SDK also includes command-line compilers for C#, C++, JScript, and VB. You use these compilers to build applications and components. These components require the runtime to execute so this is a development platform.
What is
When compiling to managed code, the compiler translates your source code into Microsoft intermediate language (MSIL), which is a CPU-independent set of instructions that can be efficiently converted to native code. MSIL includes instructions for loading, storing, initializing, and calling methods on objects, as well as instructions for arithmetic and logical operations, control flow, direct memory access, exception handling, and other operations. Microsoft intermediate language (MSIL) is a language used as the output of a number of compilers and as the input to a just-in-time (JIT) compiler. The common language runtime includes a JIT compiler for converting MSIL to native code.
Can I write IL programs directly?
Yes. Peter Drayton posted this simple example to the DOTNET mailing list:
.assembly MyAssembly {}
.class MyApp {
.method static void
.entrypoint
ldstr "Hello, IL!"
call void System.Console::WriteLine(class System.Object)
ret
}
}
Just put this into a file called hello.il, and then run ilasm hello.il. An exe assembly will be generated.
Can I do things in IL that I can't do in C#?
Yes. A couple of simple examples are that you can throw exceptions that are not derived from System.Exception, and you can have non-zero-based arrays.
What is JIT (just in time)? how it works?
Before Microsoft intermediate language (MSIL) can be executed, it must be converted by a .NET Framework just-in-time (JIT) compiler to native code, which is CPU-specific code that runs on the same computer architecture as the JIT compiler.
Rather than using time and memory to convert all the MSIL in a portable executable (PE) file to native code, it converts the MSIL as it is needed during execution and stores the resulting native code so that it is accessible for subsequent calls.
The runtime supplies another mode of compilation called install-time code generation. The install-time code generation mode converts MSIL to native code just as the regular JIT compiler does, but it converts larger units of code at a time, storing the resulting native code for use when the assembly is subsequently loaded and executed.
As part of compiling MSIL to native code, code must pass a verification process unless an administrator has established a security policy that allows code to bypass verification. Verification examines MSIL and metadata to find out whether the code can be determined to be type safe, which means that it is known to access only the memory locations it is authorized to access.
What is strong name?
A name that consists of an assembly's identity—its simple text name, version number, and culture information (if provided)—strengthened by a public key and a digital signature generated over the assembly.
What is portable executable (PE)?
The file format defining the structure that all executable files (EXE) and Dynamic Link Libraries (DLL) must use to allow them to be loaded and executed by Windows. PE is derived from the Microsoft Common Object File Format (COFF). The EXE and DLL files created using the .NET Framework obey the PE/COFF formats and also add additional header and data sections to the files that are only used by the CLR. The specification for the PE/COFF file formats is available at http://www.microsoft.com/whdc/hwdev/hardware/pecoffdown.mspx
What is Event - Delegate? clear syntax for writing a event delegate
The event keyword lets you specify a delegate that will be called upon the occurrence of some "event" in your code. The delegate can have one or more associated methods that will be called when your code indicates that the event has occurred. An event in one program can be made available to other programs that target the .NET Framework Common Language Runtime.
// keyword_delegate.cs
// delegate declaration
delegate void MyDelegate(int i);
class Program
{
public static void
{
TakesADelegate(new MyDelegate(DelegateFunction));
}
public static void TakesADelegate(MyDelegate SomeFunction)
{
SomeFunction(21);
}
public static void DelegateFunction(int i)
{
System.Console.WriteLine("Called by delegate with number: {0}.", i);
}
}
What is Code Access Security (CAS)?
CAS is the part of the .NET security model that determines whether or not a piece of code is allowed to run, and what resources it can use when it is running. For example, it is CAS that will prevent a .NET web applet from formatting your hard disk.
How does CAS work?
The CAS security policy revolves around two key concepts - code groups and permissions. Each .NET assembly is a member of a particular code group, and each code group is granted the permissions specified in a named permission set.
For example, using the default security policy, a control downloaded from a web site belongs to the 'Zone - Internet' code group, which adheres to the permissions defined by the 'Internet' named permission set. (Naturally the 'Internet' named permission set represents a very restrictive range of permissions.)
Who defines the CAS code groups?
Microsoft defines some default ones, but you can modify these and even create your own. To see the code groups defined on your system, run 'caspol -lg' from the command-line. On my syystem it looks like this:
Level = Machine
Code Groups:
1. All code: Nothing
1.1. Zone - MyComputer: FullTrust
1.1.1. Honor SkipVerification requests: SkipVerification
1.2. Zone - Intranet: LocalIntranet
1.3. Zone - Internet: Internet
1.4. Zone - Untrusted: Nothing
1.5. Zone - Trusted: Internet
1.6. StrongName - 0024000004800000940000000602000000240000525341310004000003
000000CFCB3291AA715FE99D40D49040336F9056D7886FED46775BC7BB5430BA4444FEF8348EBD06
F962F39776AE4DC3B7B04A7FE6F49F25F740423EBF2C0B89698D8D08AC48D69CED0FC8F83B465E08
07AC11EC1DCC7D054E807A43336DDE408A5393A48556123272CEEEE72F1660B71927D38561AABF5C
AC1DF1734633C602F8F2D5: Everything
Note the hierarchy of code groups - the top of the hierarchy is the most general ('All code'), which is then sub-divided into several groups, each of which in turn can be sub-divided. Also note that (somewhat counter-intuitively) a sub-group can be associated with a more permissive permission set than its parent.
How do I define my own code group?
Use caspol. For example, suppose you trust code from www.mydomain.com and you want it have full access to your system, but you want to keep the default restrictions for all other internet sites. To achieve this, you would add a new code group as a sub-group of the 'Zone - Internet' group, like this:
caspol -ag 1.3 -site www.mydomain.com FullTrust
Now if you run caspol -lg you will see that the new group has been added as group 1.3.1:
...
1.3. Zone - Internet: Internet
1.3.1. Site - www.mydomain.com: FullTrust
...
Note that the numeric label (1.3.1) is just a caspol invention to make the code groups easy to manipulate from the command-line. The underlying runtime never sees it.
How do I change the permission set for a code group?
Use caspol. If you are the machine administrator, you can operate at the 'machine' level - which means not only that the changes you make become the default for the machine, but also that users cannot change the permissions to be more permissive. If you are a normal (non-admin) user you can still modify the permissions, but only to make them more restrictive. For example, to allow intranet code to do what it likes you might do this:
caspol -cg 1.2 FullTrust
Note that because this is more permissive than the default policy (on a standard system), you should only do this at the machine level - doing it at the user level will have no effect.
Can I create my own permission set?
Yes. Use caspol -ap, specifying an XML file containing the permissions in the permission set. To save you some time, here is a sample file corresponding to the 'Everything' permission set - just edit to suit your needs. When you have edited the sample, add it to the range of available permission sets like this:
caspol -ap samplepermset.xml
Then, to apply the permission set to a code group, do something like this:
caspol -cg 1.3 SamplePermSet (By default, 1.3 is the 'Internet' code group)
I'm having some trouble with CAS. How can I diagnose my problem?
Caspol has a couple of options that might help. First, you can ask caspol to tell you what code group an assembly belongs to, using caspol -rsg. Similarly, you can ask what permissions are being applied to a particular assembly using caspol -rsp.
I can't be bothered with all this CAS stuff. Can I turn it off?
Yes, as long as you are an administrator. Just run:
caspol -s off
http://www.codeproject.com/dotnet/UB_CAS_NET.asp
Which namespace is the base class for .net Class library?
Ans: system.object
What are object pooling and connection pooling and difference? Where do we set the Min and Max Pool size for connection pooling?
Object pooling is a COM+ service that enables you to reduce the overhead of creating each object from scratch. When an object is activated, it is pulled from the pool. When the object is deactivated, it is placed back into the pool to await the next request. You can configure object pooling by applying the ObjectPoolingAttribute attribute to a class that derives from the System.EnterpriseServices.ServicedComponent class.
Object pooling lets you control the number of connections you use, as opposed to connection pooling, where you control the maximum number reached.
Following are important differences between object pooling and connection pooling:
Creation. When using connection pooling, creation is on the same thread, so if there is nothing in the pool, a connection is created on your behalf. With object pooling, the pool might decide to create a new object. However, if you have already reached your maximum, it instead gives you the next available object. This is crucial behavior when it takes a long time to create an object, but you do not use it for very long.
Enforcement of minimums and maximums. This is not done in connection pooling. The maximum value in object pooling is very important when trying to scale your application. You might need to multiplex thousands of requests to just a few objects. (TPC/C benchmarks rely on this.)
COM+ object pooling is identical to what is used in .NET Framework managed SQL Client connection pooling. For example, creation is on a different thread and minimums and maximums are enforced.
What is Application Domain?
The primary purpose of the AppDomain is to isolate an application from other applications. Win32 processes provide isolation by having distinct memory address spaces. This is effective, but it is expensive and doesn't scale well. The .NET runtime enforces AppDomain isolation by keeping control over the use of memory - all memory in the AppDomain is managed by the .NET runtime, so the runtime can ensure that AppDomains do not access each other's memory.
Objects in different application domains communicate either by transporting copies of objects across application domain boundaries, or by using a proxy to exchange messages.
MarshalByRefObject is the base class for objects that communicate across application domain boundaries by exchanging messages using a proxy. Objects that do not inherit from MarshalByRefObject are implicitly marshal by value. When a remote application references a marshal by value object, a copy of the object is passed across application domain boundaries.
How does an AppDomain get created?
AppDomains are usually created by hosts. Examples of hosts are the Windows Shell, ASP.NET and IE. When you run a .NET application from the command-line, the host is the Shell. The Shell creates a new AppDomain for every application.
AppDomains can also be explicitly created by .NET applications. Here is a C# sample which creates an AppDomain, creates an instance of an object inside it, and then executes one of the object's methods. Note that you must name the executable 'appdomaintest.exe' for this code to work as-is.
using System;
using System.Runtime.Remoting;
public class CAppDomainInfo : MarshalByRefObject
{
public string GetAppDomainInfo()
{
return "AppDomain = " + AppDomain.CurrentDomain.FriendlyName;
}
}
public class App
{
public static int
{
AppDomain ad = AppDomain.CreateDomain( "Andy's new domain", null, null );
ObjectHandle oh = ad.CreateInstance( "appdomaintest", "CAppDomainInfo" );
CAppDomainInfo adInfo = (CAppDomainInfo)(oh.Unwrap());
string info = adInfo.GetAppDomainInfo();
Console.WriteLine( "AppDomain info: " + info );
return 0;
}
}
What is serialization in .NET? What are the ways to control serialization?
Serialization is the process of converting an object into a stream of bytes. Deserialization is the opposite process of creating an object from a stream of bytes. Serialization/Deserialization is mostly used to transport objects (e.g. during remoting), or to persist objects (e.g. to a file or database).Serialization can be defined as the process of storing the state of an object to a storage medium. During this process, the public and private fields of the object and the name of the class, including the assembly containing the class, are converted to a stream of bytes, which is then written to a data stream. When the object is subsequently deserialized, an exact clone of the original object is created.
Binary serialization preserves type fidelity, which is useful for preserving the state of an object between different invocations of an application. For example, you can share an object between different applications by serializing it to the clipboard. You can serialize an object to a stream, disk, memory, over the network, and so forth. Remoting uses serialization to pass objects "by value" from one computer or application domain to another.
XML serialization serializes only public properties and fields and does not preserve type fidelity. This is useful when you want to provide or consume data without restricting the application that uses the data. Because XML is an open standard, it is an attractive choice for sharing data across the Web. SOAP is an open standard, which makes it an attractive choice.
There are two separate mechanisms provided by the .NET class library - XmlSerializer and SoapFormatter/BinaryFormatter. Microsoft uses XmlSerializer for Web Services, and uses SoapFormatter/BinaryFormatter for remoting. Both are available for use in your own code.
Why do I get errors when I try to serialize a Hashtable?
XmlSerializer will refuse to serialize instances of any class that implements IDictionary, e.g. Hashtable. SoapFormatter and BinaryFormatter do not have this restriction.
What is exception handling?
When an exception occurs, the system searches for the nearest catch clause that can handle the exception, as determined by the run-time type of the exception. First, the current method is searched for a lexically enclosing try statement, and the associated catch clauses of the try statement are considered in order. If that fails, the method that called the current method is searched for a lexically enclosing try statement that encloses the point of the call to the current method. This search continues until a catch clause is found that can handle the current exception, by naming an exception class that is of the same class, or a base class, of the run-time type of the exception being thrown. A catch clause that doesn't name an exception class can handle any exception.
Once a matching catch clause is found, the system prepares to transfer control to the first statement of the catch clause. Before execution of the catch clause begins, the system first executes, in order, any finally clauses that were associated with try statements more nested that than the one that caught the exception.
Exceptions that occur during destructor execution are worth special mention. If an exception occurs during destructor execution, and that exception is not caught, then the execution of that destructor is terminated and the destructor of the base class (if any) is called. If there is no base class (as in the case of the object type) or if there is no base class destructor, then the exception is discarded.
What is Assembly?
Assemblies are the building blocks of .NET Framework applications; they form the fundamental unit of deployment, version control, reuse, activation scoping, and security permissions. An assembly is a collection of types and resources that are built to work together and form a logical unit of functionality. An assembly provides the common language runtime with the information it needs to be aware of type implementations. To the runtime, a type does not exist outside the context of an assembly.
Assemblies are a fundamental part of programming with the .NET Framework. An assembly performs the following functions:
It contains code that the common language runtime executes. Microsoft intermediate language (MSIL) code in a portable executable (PE) file will not be executed if it does not have an associated assembly manifest. Note that each assembly can have only one entry point (that is, DllMain, WinMain, or
It forms a security boundary. An assembly is the unit at which permissions are requested and granted.
It forms a type boundary. Every type's identity includes the name of the assembly in which it resides. A type called MyType loaded in the scope of one assembly is not the same as a type called MyType loaded in the scope of another assembly.
It forms a reference scope boundary. The assembly's manifest contains assembly metadata that is used for resolving types and satisfying resource requests. It specifies the types and resources that are exposed outside the assembly. The manifest also enumerates other assemblies on which it depends.
It forms a version boundary. The assembly is the smallest versionable unit in the common language runtime; all types and resources in the same assembly are versioned as a unit. The assembly's manifest describes the version dependencies you specify for any dependent assemblies.
It forms a deployment unit. When an application starts, only the assemblies that the application initially calls must be present. Other assemblies, such as localization resources or assemblies containing utility classes, can be retrieved on demand. This allows applications to be kept simple and thin when first downloaded.
It is the unit at which side-by-side execution is supported.
Assemblies can be static or dynamic. Static assemblies can include .NET Framework types (interfaces and classes), as well as resources for the assembly (bitmaps, JPEG files, resource files, and so on). Static assemblies are stored on disk in PE files. You can also use the .NET Framework to create dynamic assemblies, which are run directly from memory and are not saved to disk before execution. You can save dynamic assemblies to disk after they have executed.
There are several ways to create assemblies. You can use development tools, such as Visual Studio .NET, that you have used in the past to create .dll or .exe files. You can use tools provided in the .NET Framework SDK to create assemblies with modules created in other development environments. You can also use common language runtime APIs, such as Reflection.Emit, to create dynamic assemblies.
What are the contents of assembly?
In general, a static assembly can consist of four elements:
The assembly manifest, which contains assembly metadata.
Type metadata.
Microsoft intermediate language (MSIL) code that implements the types.
A set of resources.
What are the different types of assemblies?
Private, Public/Shared, Satellite
What is the difference between a private assembly and a shared assembly?
Location and visibility: A private assembly is normally used by a single application, and is stored in the application's directory, or a sub-directory beneath. A shared assembly is normally stored in the global assembly cache, which is a repository of assemblies maintained by the .NET runtime. Shared assemblies are usually libraries of code which many applications will find useful, e.g. the .NET framework classes.
Versioning: The runtime enforces versioning constraints only on shared assemblies, not on private assemblies.
What are Satellite Assemblies? How you will create this? How will you get the different language strings?
Satellite assemblies are often used to deploy language-specific resources for an application. These language-specific assemblies work in side-by-side execution because the application has a separate product ID for each language and installs satellite assemblies in a language-specific subdirectory for each language. When uninstalling, the application removes only the satellite assemblies associated with a given language and .NET Framework version. No core .NET Framework files are removed unless the last language for that .NET Framework version is being removed.
(For example, English and Japanese editions of the .NET Framework version 1.1 share the same core files. The Japanese .NET Framework version 1.1 adds satellite assemblies with localized resources in a \ja subdirectory. An application that supports the .NET Framework version 1.1, regardless of its language, always uses the same core runtime files.)
http://www.ondotnet.com/lpt/a/2637
**
How will u load dynamic assembly? How will create assemblies at run time?
**
What is Assembly manifest? what all details the assembly manifest will contain?
Every assembly, whether static or dynamic, contains a collection of data that describes how the elements in the assembly relate to each other. The assembly manifest contains this assembly metadata. An assembly manifest contains all the metadata needed to specify the assembly's version requirements and security identity, and all metadata needed to define the scope of the assembly and resolve references to resources and classes. The assembly manifest can be stored in either a PE file (an .exe or .dll) with Microsoft intermediate language (MSIL) code or in a standalone PE file that contains only assembly manifest information.
It contains Assembly name, Version number, Culture, Strong name information, List of all files in the assembly, Type reference information, Information on referenced assemblies.
Difference between assembly manifest & metadata?
assembly manifest - An integral part of every assembly that renders the assembly self-describing. The assembly manifest contains the assembly's metadata. The manifest establishes the assembly identity, specifies the files that make up the assembly implementation, specifies the types and resources that make up the assembly, itemizes the compile-time dependencies on other assemblies, and specifies the set of permissions required for the assembly to run properly. This information is used at run time to resolve references, enforce version binding policy, and validate the integrity of loaded assemblies. The self-describing nature of assemblies also helps makes zero-impact install and XCOPY deployment feasible.
metadata - Information that describes every element managed by the common language runtime: an assembly, loadable file, type, method, and so on. This can include information required for debugging and garbage collection, as well as security attributes, marshaling data, extended class and member definitions, version binding, and other information required by the runtime.
What is Global Assembly Cache (GAC) and what is the purpose of it? (How to make an assembly to public? Steps) How more than one version of an assembly can keep in same place?
Each computer where the common language runtime is installed has a machine-wide code cache called the global assembly cache. The global assembly cache stores assemblies specifically designated to be shared by several applications on the computer. You should share assemblies by installing them into the global assembly cache only when you need to.
Steps
- Create a strong name using sn.exe tool
eg: sn -k keyPair.snk
- with in AssemblyInfo.cs add the generated file name
eg: [assembly: AssemblyKeyFile("abc.snk")]
- recompile project, then install it to GAC by either
drag & drop it to assembly folder (C:\WINDOWS\assembly OR C:\WINNT\assembly) (shfusion.dll tool)
or
gacutil -i abc.dll
If I have more than one version of one assemblies, then how'll I use old version (how/where to specify version number?)in my application?
**
How to find methods of a assembly file (not using ILDASM)
Reflection
What is Garbage Collection in .Net? Garbage collection process?
The process of transitively tracing through all pointers to actively used objects in order to locate all objects that can be referenced, and then arranging to reuse any heap memory that was not found during this trace. The common language runtime garbage collector also compacts the memory that is in use to reduce the working space needed for the heap.
What is Reflection in .NET? Namespace? How will you load an assembly which is not referenced by current assembly?
All .NET compilers produce metadata about the types defined in the modules they produce. This metadata is packaged along with the module (modules in turn are packaged together in assemblies), and can be accessed by a mechanism called reflection. The System.Reflection namespace contains classes that can be used to interrogate the types for a module/assembly.
Using reflection to access .NET metadata is very similar to using ITypeLib/ITypeInfo to access type library data in COM, and it is used for similar purposes - e.g. determining data type sizes for marshaling data across context/process/machine boundaries.
Reflection can also be used to dynamically invoke methods (see System.Type.InvokeMember), or even create types dynamically at run-time (see System.Reflection.Emit.TypeBuilder).
What is Custom attribute? How to create? If I'm having custom attribute in an assembly, how to say that name in the code?
A: The primary steps to properly design custom attribute classes are as follows:
Applying the AttributeUsageAttribute ([AttributeUsage(AttributeTargets.All, Inherited = false, AllowMultiple = true)])
Declaring the attribute. (class public class MyAttribute : System.Attribute { // . . . })
Declaring constructors (public MyAttribute(bool myvalue) { this.myvalue = myvalue; })
Declaring properties
public bool MyProperty
{
get {return this.myvalue;}
set {this.myvalue = value;}
}
The following example demonstrates the basic way of using reflection to get access to custom attributes.
class MainClass
{
public static void
{
System.Reflection.MemberInfo info = typeof(MyClass);
object[] attributes = info.GetCustomAttributes();
for (int i = 0; i < attributes.Length; i ++)
{
System.Console.WriteLine(attributes[i]);
}
}
}
What is the managed and unmanaged code in .net?
The .NET Framework provides a run-time environment called the Common Language Runtime, which manages the execution of code and provides services that make the development process easier. Compilers and tools expose the runtime's functionality and enable you to write code that benefits from this managed execution environment. Code that you develop with a language compiler that targets the runtime is called managed code; it benefits from features such as cross-language integration, cross-language exception handling, enhanced security, versioning and deployment support, a simplified model for component interaction, and debugging and profiling services.
How do you create threading in .NET? What is the namespace for that?
**
System.Threading.Thread
Serialize and MarshalByRef?
using directive vs using statement
You create an instance in a using statement to ensure that Dispose is called on the object when the using statement is exited. A using statement can be exited either when the end of the using statement is reached or if, for example, an exception is thrown and control leaves the statement block before the end of the statement.
The using directive has two uses:
Create an alias for a namespace (a using alias).
Permit the use of types in a namespace, such that, you do not have to qualify the use of a type in that namespace (a using directive).
Describe the Managed Execution Process?
The managed execution process includes the following steps:
Choosing a compiler.
To obtain the benefits provided by the common language runtime, you must use one or more language compilers that target the runtime.
Compiling your code to Microsoft intermediate language (MSIL).
Compiling translates your source code into MSIL and generates the required metadata.
Compiling MSIL to native code.
At execution time, a just-in-time (JIT) compiler translates the MSIL into native code. During this compilation, code must pass a verification process that examines the MSIL and metadata to find out whether the code can be determined to be type safe.
Executing your code.
The common language runtime provides the infrastructure that enables execution to take place as well as a variety of services that can be used during execution.
What is Active Directory? What is the namespace used to access the Microsoft Active Directories? What are ADSI Directories?
Active Directory Service Interfaces (ADSI) is a programmatic interface for Microsoft Windows Active Directory. It enables your applications to interact with diverse directories on a network, using a single interface. Visual Studio .NET and the .NET Framework make it easy to add ADSI functionality with the DirectoryEntry and DirectorySearcher components.
Using ADSI, you can create applications that perform common administrative tasks, such as backing up databases, accessing printers, and administering user accounts. ADSI makes it possible for you to:
Log on once to work with diverse directories. The DirectoryEntry component class provides username and password properties that can be entered at runtime and communicated to the Active Directory object you are binding to.
Use a single application programming interface (API) to perform tasks on multiple directory systems by offering the user a variety of protocols to use. The DirectoryServices namespace provides the classes to perform most administrative functions.
Perform "rich querying" on directory systems. ADSI technology allows for searching for an object by specifying two query dialects: SQL and LDAP.
Access and use a single, hierarchical structure for administering and maintaining diverse and complicated network configurations by accessing an Active Directory tree.
Integrate directory information with databases such as SQL Server. The DirectoryEntry path may be used as an ADO.NET connection string provided that it is using the LDAP provider.
using System.DirectoryServices;
How Garbage Collector (GC) Works?
The methods in this class influence when an object is garbage collected and when resources allocated by an object are released. Properties in this class provide information about the total amount of memory available in the system and the age category, or generation, of memory allocated to an object. Periodically, the garbage collector performs garbage collection to reclaim memory allocated to objects for which there are no valid references. Garbage collection happens automatically when a request for memory cannot be satisfied using available free memory. Alternatively, an application can force garbage collection using the Collect method.
Garbage collection consists of the following steps:
The garbage collector searches for managed objects that are referenced in managed code.
The garbage collector attempts to finalize objects that are not referenced.
The garbage collector frees objects that are not referenced and reclaims their memory.
Why do we need to call CG.SupressFinalize?
Requests that the system not call the finalizer method for the specified object.
[C#]
public static void SuppressFinalize(
object obj
); The method removes obj from the set of objects that require finalization. The obj parameter is required to be the caller of this method.
Objects that implement the IDisposable interface can call this method from the IDisposable.Dispose method to prevent the garbage collector from calling Object.Finalize on an object that does not require it.
What is nmake tool?
The Nmake tool (Nmake.exe) is a 32-bit tool that you use to build projects based on commands contained in a .mak file.
usage : nmake -a all
What are Namespaces?
The namespace keyword is used to declare a scope. This namespace scope lets you organize code and gives you a way to create globally-unique types. Even if you do not explicitly declare one, a default namespace is created. This unnamed namespace, sometimes called the global namespace, is present in every file. Any identifier in the global namespace is available for use in a named namespace. Namespaces implicitly have public access and this is not modifiable.
What is the difference between CONST and READONLY?
Both are meant for constant values. A const field can only be initialized at the declaration of the field. A readonly field can be initialized either at the declaration or in a constructor. Therefore, readonly fields can have different values depending on the constructor used.
readonly int b;
public X()
{
b=1;
}
public X(string s)
{
b=5;
}
public X(string s, int i)
{
b=i;
}
Also, while a const field is a compile-time constant, the readonly field can be used for runtime constants, as in the following example:
public static readonly uint l1 = (uint) DateTime.Now.Ticks; (this can't be possible with const)
What is the difference between ref & out parameters?
An argument passed to a ref parameter must first be initialized. Compare this to an out parameter, whose argument does not have to be explicitly initialized before being passed to an out parameter.
What is the difference between Array and LinkedList?
What is the difference between Array and Arraylist?
As elements are added to an ArrayList, the capacity is automatically increased as required through reallocation. The capacity can be decreased by calling TrimToSize or by setting the Capacity property explicitly.
What is Jagged Arrays?
A jagged array is an array whose elements are arrays. The elements of a jagged array can be of different dimensions and sizes. A jagged array is sometimes called an "array-of-arrays."
What are indexers?
Indexers are similar to properties, except that the get and set accessors of indexers take parameters, while property accessors do not.
What is Asynchronous call and how it can be implemented using delegates?
How to create events for a control? What is custom events? How to create it?
If you want to write your own dot net language, what steps you will u take care?
Describe the difference between inline and code behind - which is best in a loosely coupled solution?
how dot net compiled code will become platform independent?
without modifying source code if we compile again, will it be generated MSIL again?
C++ & C# differences
**
(COM)
Interop Services?
The common language runtime provides two mechanisms for interoperating with unmanaged code:
Platform invoke, which enables managed code to call functions exported from an unmanaged library.
COM interop, which enables managed code to interact with COM objects through interfaces.
Both platform invoke and COM interop use interop marshaling to accurately move method arguments between caller and callee and back, if required.
How does u handle this COM components developed in other programming languages in .NET?
What is RCW (Runtime Callable Wrappers)?
The common language runtime exposes COM objects through a proxy called the runtime callable wrapper (RCW). Although the RCW appears to be an ordinary object to .NET clients, its primary function is to marshal calls between a .NET client and a COM object.
What is CCW (COM Callable Wrapper)
A proxy object generated by the common language runtime so that existing COM applications can use managed classes, including .NET Framework classes, transparently.
How CCW and RCW is working?
**
How will you register com+ services?
The .NET Framework SDK provides the .NET Framework Services Installation Tool (Regsvcs.exe - a command-line tool) to manually register an assembly containing serviced components. You can also access these registration features programmatically with the System.EnterpriseServicesRegistrationHelper class by creating an instance of class RegistrationHelper and using the method InstallAssembly
What is use of ContextUtil class?
ContextUtil is the preferred class to use for obtaining COM+ context information.
What is the new three features of COM+ services, which are not there in COM (MTS)?
**
Is the COM architecture same as .Net architecture? What is the difference between them?
**
Can we copy a COM dll to GAC folder?
**
What is Pinvoke?
Platform invoke is a service that enables managed code to call unmanaged functions implemented in dynamic-link libraries (DLLs), such as those in the Win32 API. It locates and invokes an exported function and marshals its arguments (integers, strings, arrays, structures, and so on) across the interoperation boundary as needed.
Is it true that COM objects no longer need to be registered on the server?
Answer: Yes and No. Legacy COM objects still need to be registered on the server before they can be used. COM developed using the new .NET Framework will not need to be registered. Developers will be able to auto-register these objects just by placing them in the 'bin' folder of the application.
Can .NET Framework components use the features of Component Services?
Answer: Yes, you can use the features and functions of Component Services from a .NET Framework component.
Advantage of ADO.Net?
ADO.NET Does Not Depend On Continuously Live Connections
Database Interactions Are Performed Using Data Commands
Data Can Be Cached in Datasets
Datasets Are Independent of Data Sources
Data Is Persisted as XML
Schemas Define Data Structures
How would u connect to database using .NET?
SqlConnection nwindConn = new SqlConnection("Data Source=localhost; Integrated Security=SSPI;" +
"Initial Catalog=northwind");
nwindConn.Open();
What are relation objects in dataset and how & where to use them?
In a DataSet that contains multiple DataTable objects, you can use DataRelation objects to relate one table to another, to navigate through the tables, and to return child or parent rows from a related table. Adding a DataRelation to a DataSet adds, by default, a UniqueConstraint to the parent table and a ForeignKeyConstraint to the child table.
The following code example creates a DataRelation using two DataTable objects in a DataSet. Each DataTable contains a column named CustID, which serves as a link between the two DataTable objects. The example adds a single DataRelation to the Relations collection of the DataSet. The first argument in the example specifies the name of the DataRelation being created. The second argument sets the parent DataColumn and the third argument sets the child DataColumn.
custDS.Relations.Add("CustOrders",
custDS.Tables["Customers"].Columns["CustID"],
custDS.Tables["Orders"].Columns["CustID"]);
OR
private void CreateRelation()
{
// Get the DataColumn objects from two DataTable objects in a DataSet.
DataColumn parentCol;
DataColumn childCol;
// Code to get the DataSet not shown here.
parentCol = DataSet1.Tables["Customers"].Columns["CustID"];
childCol = DataSet1.Tables["Orders"].Columns["CustID"];
// Create DataRelation.
DataRelation relCustOrder;
relCustOrder = new DataRelation("CustomersOrders", parentCol, childCol);
// Add the relation to the DataSet.
DataSet1.Relations.Add(relCustOrder);
}
Difference between OLEDB Provider and SqlClient ?
Ans: SQLClient .NET classes are highly optimized for the .net / sqlserver combination and achieve optimal results. The SqlClient data provider is fast. It's faster than the Oracle provider, and faster than accessing database via the OleDb layer. It's faster because it accesses the native library (which automatically gives you better performance), and it was written with lots of help from the SQL Server team.
What are the different namespaces used in the project to connect the database? What data providers available in .net to connect to database?
System.Data.OleDb – classes that make up the .NET Framework Data Provider for OLE DB-compatible data sources. These classes allow you to connect to an OLE DB data source, execute commands against the source, and read the results.
System.Data.SqlClient – classes that make up the .NET Framework Data Provider for SQL Server, which allows you to connect to SQL Server 7.0, execute commands, and read results. The System.Data.SqlClient namespace is similar to the System.Data.OleDb namespace, but is optimized for access to SQL Server 7.0 and later.
System.Data.Odbc - classes that make up the .NET Framework Data Provider for ODBC. These classes allow you to access ODBC data source in the managed space.
System.Data.OracleClient - classes that make up the .NET Framework Data Provider for Oracle. These classes allow you to access an Oracle data source in the managed space.
Difference between DataReader and DataAdapter / DataSet and DataAdapter?
You can use the ADO.NET DataReader to retrieve a read-only, forward-only stream of data from a database. Using the DataReader can increase application performance and reduce system overhead because only one row at a time is ever in memory.
After creating an instance of the Command object, you create a DataReader by calling Command.ExecuteReader to retrieve rows from a data source, as shown in the following example.
SqlDataReader myReader = myCommand.ExecuteReader();
You use the Read method of the DataReader object to obtain a row from the results of the query.
while (myReader.Read())
Console.WriteLine("\t{0}\t{1}", myReader.GetInt32(0), myReader.GetString(1));
myReader.Close();
The DataSet is a memory-resident representation of data that provides a consistent relational programming model regardless of the data source. It can be used with multiple and differing data sources, used with XML data, or used to manage data local to the application. The DataSet represents a complete set of data including related tables, constraints, and relationships among the tables. The methods and objects in a DataSet are consistent with those in the relational database model. The DataSet can also persist and reload its contents as XML and its schema as XML Schema definition language (XSD) schema.
The DataAdapter serves as a bridge between a DataSet and a data source for retrieving and saving data. The DataAdapter provides this bridge by mapping Fill, which changes the data in the DataSet to match the data in the data source, and Update, which changes the data in the data source to match the data in the DataSet. If you are connecting to a Microsoft SQL Server database, you can increase overall performance by using the SqlDataAdapter along with its associated SqlCommand and SqlConnection. For other OLE DB-supported databases, use the DataAdapter with its associated OleDbCommand and OleDbConnection objects.
Which method do you invoke on the DataAdapter control to load your generated dataset with data?
Fill()
Explain different methods and Properties of DataReader which you have used in your project?
Read
GetString
GetInt32
while (myReader.Read())
Console.WriteLine("\t{0}\t{1}", myReader.GetInt32(0), myReader.GetString(1));
myReader.Close();
What happens when we issue Dataset.ReadXml command?
Reads XML schema and data into the DataSet.
In how many ways we can retrieve table records count? How to find the count of records in a dataset?
foreach(DataTable thisTable in myDataSet.Tables){
// For each row, print the values of each column.
foreach(DataRow myRow in thisTable.Rows){
How to check if a datareader is closed or opened?
IsClosed()
What happens when u try to update data in a dataset in .NET while the record is already deleted in SQL SERVER as backend?
OR What is concurrency? How will you avoid concurrency when dealing with dataset? (One user deleted one row after that another user through his dataset was trying to update same row. What will happen? How will you avoid the problem?)
**
How do you merge 2 datasets into the third dataset in a simple manner? OR If you are executing these statements in commandObject. "Select * from Table1;Select * from Table2” how you will deal result set?
**
How do you sort a dataset?
**
If a dataset contains 100 rows, how to fetch rows between 5 and 15 only?
**
Differences between dataset.clone and dataset.copy?
Clone - Copies the structure of the DataSet, including all DataTable schemas, relations, and constraints. Does not copy any data.
Copy - Copies both the structure and data for this DataSet.
What is the use of parameter object?
**
How to generate XML from a dataset and vice versa?
**
What is method to get XML and schema from Dataset?
ans: getXML () and get Schema ()
How do u implement locking concept for dataset?
What are server controls?
ASP.NET server controls are components that run on the server and encapsulate user-interface and other related functionality. They are used in ASP.NET pages and in ASP.NET code-behind classes.
What is the difference between Web User Control and Web Custom Control?
Custom Controls
Web custom controls are compiled components that run on the server and that encapsulate user-interface and other related functionality into reusable packages. They can include all the design-time features of standard ASP.NET server controls, including full support for Visual Studio design features such as the Properties window, the visual designer, and the Toolbox.
There are several ways that you can create Web custom controls:
You can compile a control that combines the functionality of two or more existing controls. For example, if you need a control that encapsulates a button and a text box, you can create it by compiling the existing controls together.
If an existing server control almost meets your requirements but lacks some required features, you can customize the control by deriving from it and overriding its properties, methods, and events.
If none of the existing Web server controls (or their combinations) meet your requirements, you can create a custom control by deriving from one of the base control classes. These classes provide all the basic functionality of Web server controls, so you can focus on programming the features you need.
If none of the existing ASP.NET server controls meet the specific requirements of your applications, you can create either a Web user control or a Web custom control that encapsulates the functionality you need. The main difference between the two controls lies in ease of creation vs. ease of use at design time.
Web user controls are easy to make, but they can be less convenient to use in advanced scenarios. You develop Web user controls almost exactly the same way that you develop Web Forms pages. Like Web Forms, user controls can be created in the visual designer, they can be written with code separated from the HTML, and they can handle execution events. However, because Web user controls are compiled dynamically at run time they cannot be added to the Toolbox, and they are represented by a simple placeholder glyph when added to a page. This makes Web user controls harder to use if you are accustomed to full Visual Studio .NET design-time support, including the Properties window and Design view previews. Also, the only way to share the user control between applications is to put a separate copy in each application, which takes more maintenance if you make changes to the control.
Web custom controls are compiled code, which makes them easier to use but more difficult to create; Web custom controls must be authored in code. Once you have created the control, however, you can add it to the Toolbox and display it in a visual designer with full Properties window support and all the other design-time features of ASP.NET server controls. In addition, you can install a single copy of the Web custom control in the global assembly cache and share it between applications, which makes maintenance easier.
| Web user controls | Web custom controls |
| Easier to create | Harder to create |
| Limited support for consumers who use a visual design tool | Full visual design tool support for consumers |
| A separate copy of the control is required in each application | Only a single copy of the control is required, in the global assembly cache |
| Cannot be added to the Toolbox in Visual Studio | Can be added to the Toolbox in Visual Studio |
| Good for static layout | Good for dynamic layout |
(Session/State)
Application and Session Events
The ASP.NET page framework provides ways for you to work with events that can be raised when your application starts or stops or when an individual user's session starts or stops:
Application events are raised for all requests to an application. For example, Application_BeginRequest is raised when any Web Forms page or XML Web service in your application is requested. This event allows you to initialize resources that will be used for each request to the application. A corresponding event, Application_EndRequest, provides you with an opportunity to close or otherwise dispose of resources used for the request.
Session events are similar to application events (there is a Session_OnStart and a Session_OnEnd event), but are raised with each unique session within the application. A session begins when a user requests a page for the first time from your application and ends either when your application explicitly closes the session or when the session times out.
You can create handlers for these types of events in the Global.asax file.
Difference between ASP Session and ASP.NET Session?
asp.net session supports cookie less session & it can span across multiple servers.
What is cookie less session? How it works?
By default, ASP.NET will store the session state in the same process that processes the request, just as ASP does. If cookies are not available, a session can be tracked by adding a session identifier to the URL. This can be enabled by setting the following:
http://samples.gotdotnet.com/quickstart/aspplus/doc/stateoverview.aspx
How you will handle session when deploying application in more than a server? Describe session handling in a webfarm, how does it work and what are the limits?
By default, ASP.NET will store the session state in the same process that processes the request, just as ASP does. Additionally, ASP.NET can store session data in an external process, which can even reside on another machine. To enable this feature:
Start the ASP.NET state service, either using the Services snap-in or by executing "net start aspnet_state" on the command line. The state service will by default listen on port 42424. To change the port, modify the registry key for the service: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\aspnet_state\Parameters\Port
Set the mode attribute of the
Configure the stateConnectionString attribute with the values of the machine on which you started aspnet_state.
The following sample assumes that the state service is running on the same machine as the Web server ("localhost") and uses the default port (42424):
Note that if you try the sample above with this setting, you can reset the Web server (enter iisreset on the command line) and the session state value will persist.
**
What method do you use to explicitly kill a users session?
Abandon()
What are the different ways you would consider sending data across pages in ASP (i.e between 1.asp to 2.asp)?
Session
public properties
What is State Management in .Net and how many ways are there to maintain a state in .Net? What is view state?
Web pages are recreated each time the page is posted to the server. In traditional Web programming, this would ordinarily mean that all information associated with the page and the controls on the page would be lost with each round trip.
To overcome this inherent limitation of traditional Web programming, the ASP.NET page framework includes various options to help you preserve changes — that is, for managing state. The page framework includes a facility called view state that automatically preserves property values of the page and all the controls on it between round trips.
However, you will probably also have application-specific values that you want to preserve. To do so, you can use one of the state management options.
Client-Based State Management Options:
Hidden Form Fields
Cookies
Query Strings
Server-Based
Database Support
What are the disadvantages of view state / what are the benefits?
Automatic view-state management is a feature of server controls that enables them to repopulate their property values on a round trip (without you having to write any code). This feature does impact performance, however, since a server control's view state is passed to and from the server in a hidden form field. You should be aware of when view state helps you and when it hinders your page's performance.
When maintaining session through Sql server, what is the impact of Read and Write operation on Session objects? will performance degrade?
Maintaining state using database technology is a common practice when storing user-specific information where the information store is large. Database storage is particularly useful for maintaining long-term state or state that must be preserved even if the server must be restarted.
**
What are the contents of cookie?
**
How do you create a permanent cookie?
**
What is ViewState? What does the "EnableViewState" property do? Why would I want it on or off?
**
Explain the differences between Server-side and Client-side code?
Server side code will process at server side & it will send the result to client. Client side code (javascript) will execute only at client side.
Can you give an example of what might be best suited to place in the Application_Start and Session_Start subroutines?
**
Which ASP.NET configuration options are supported in the ASP.NET implementation on the shared web hosting platform?
A: Many of the ASP.NET configuration options are not configurable at the site, application or subdirectory level on the shared hosting platform. Certain options can affect the security, performance and stability of the server and, therefore cannot be changed. The following settings are the only ones that can be changed in your site’s web.config file (s):
browserCaps
clientTarget
pages
customErrors
globalization
authorization
authentication
webControls
webServices
What is disco file?
What’s the attribute for webservice method? What is the namespace for creating webservice?
[WebMethod]
using System.Web;
using System.Web.Services;
What is Remoting?
The process of communication between different operating system processes, regardless of whether they are on the same computer. The .NET remoting system is an architecture designed to simplify communication between objects living in different application domains, whether on the same computer or not, and between different contexts, whether in the same application domain or not.
Difference between web services & remoting?
|
| ASP.NET Web Services | .NET Remoting |
| Protocol | Can be accessed only over HTTP | Can be accessed over any protocol (including TCP, HTTP, SMTP and so on) |
| State Management | Web services work in a stateless environment | Provide support for both stateful and stateless environments through Singleton and SingleCall objects |
| Type System | Web services support only the datatypes defined in the XSD type system, limiting the number of objects that can be serialized. | Using binary communication, .NET Remoting can provide support for rich type system |
| Interoperability | Web services support interoperability across platforms, and are ideal for heterogeneous environments. | .NET remoting requires the client be built using .NET, enforcing homogenous environment. |
| Reliability | Highly reliable due to the fact that Web services are always hosted in IIS | Can also take advantage of IIS for fault isolation. If IIS is not used, application needs to provide plumbing for ensuring the reliability of the application. |
| Extensibility | Provides extensibility by allowing us to intercept the SOAP messages during the serialization and deserialization stages. | Very extensible by allowing us to customize the different components of the .NET remoting framework. |
| Ease-of-Programming | Easy-to-create and deploy. | Complex to program. |
Though both the .NET Remoting infrastructure and ASP.NET Web services can enable cross-process communication, each is designed to benefit a different target audience. ASP.NET Web services provide a simple programming model and a wide reach. .NET Remoting provides a more complex programming model and has a much narrower reach.
As explained before, the clear performance advantage provided by TCPChannel-remoting should make you think about using this channel whenever you can afford to do so. If you can create direct TCP connections from your clients to your server and if you need to support only the .NET platform, you should go for this channel. If you are going to go cross-platform or you have the requirement of supporting SOAP via HTTP, you should definitely go for ASP.NET Web services.
Both the .NET remoting and ASP.NET Web services are powerful technologies that provide a suitable framework for developing distributed applications. It is important to understand how both technologies work and then choose the one that is right for your application. For applications that require interoperability and must function over public networks, Web services are probably the best bet. For those that require communications with other .NET components and where performance is a key priority, .NET Remoting is the best choice. In short, use Web services when you need to send and receive data from different computing platforms, use .NET Remoting when sending and receiving data between .NET applications. In some architectural scenarios, you might also be able to use.NET Remoting in conjunction with ASP.NET Web services and take advantage of the best of both worlds.
The Key difference between ASP.NET webservices and .NET Remoting is how they serialize data into messages and the format they choose for metadata. ASP.NET uses XML serializer for serializing or Marshalling. And XSD is used for Metadata. .NET Remoting relies on System.Runtime.Serialization.Formatter.Binary and System.Runtime.Serialization.SOAPFormatter and relies on .NET CLR Runtime assemblies for metadata.
Can you pass SOAP messages through remoting?
CAO and SAO.
Client Activated objects are those remote objects whose Lifetime is directly Controlled by the client. This is in direct contrast to SAO. Where the server, not the client has complete control over the lifetime of the objects.
Client activated objects are instantiated on the server as soon as the client request the object to be created. Unlike as SAO a CAO doesn’t delay the object creation until the first method is called on the object. (In SAO the object is instantiated when the client calls the method on the object)
singleton and singlecall.
Singleton types never have more than one instance at any one time. If an instance exists, all client requests are serviced by that instance.
Single Call types always have one instance per client request. The next method invocation will be serviced by a different server instance, even if the previous instance has not yet been recycled by the system.
What is Asynchronous Web Services?
Web Client class and its methods?
Flow of remoting?
What is the use of trace utility?
Using the SOAP Trace Utility
The Microsoft® Simple Object Access Protocol (SOAP) Toolkit 2.0 includes a TCP/IP trace utility, MSSOAPT.EXE. You use this trace utility to view the SOAP messages sent by HTTP between a SOAP client and a service on the server.
Using the Trace Utility on the Server
To see all of a service's messages received from and sent to all clients, perform the following steps on the server.
On the server, open the Web Services Description Language (WSDL) file.
In the WSDL file, locate the
Run MSSOAPT.exe.
On the File menu, point to New, and either click Formatted Trace (if you don't want to see HTTP headers) or click Unformatted Trace (if you do want to see HTTP headers).
In the Trace Setup dialog box, click OK to accept the default values.
Using the Trace Utility on the Client
To see all messages sent to and received from a service, do the following steps on the client.
Copy the WSDL file from the server to the client.
Modify location attribute of the
On the client, run MSSOPT.exe.
On the File menu, point to New, and either click Formatted Trace (if you don't want to see HTTP headers) or click Unformatted Trace (if you do want to see HTTP headers).
In the Destination host box, enter the host specified in Step 2.
In the Destination port box, enter the port specified in Step 2.
Click OK.
In which process does IIS runs (was asking about the EXE file)
inetinfo.exe is the Microsoft IIS server running, handling ASP.NET requests among other things. When an ASP.NET request is received (usually a file with .aspx extension), the ISAPI filter aspnet_isapi.dll takes care of it by passing the request to the actual worker process aspnet_wp.exe.
Where are the IIS log files stored?
C:\WINDOWS\system32\Logfiles\W3SVC1
OR
c:\winnt\system32\LogFiles\W3SVC1
What are the different IIS authentication modes in IIS 5.0 and Explain? Difference between basic and digest authentication modes?
IIS provides a variety of authentication schemes:
Anonymous (enabled by default)
Basic
Digest
Integrated Windows authentication (enabled by default)
Client Certificate Mapping
Anonymous
Anonymous authentication gives users access to the public areas of your Web site without prompting them for a user name or password. Although listed as an authentication scheme, it is not technically performing any client authentication because the client is not required to supply any credentials. Instead, IIS provides stored credentials to Windows using a special user account, IUSR_machinename. By default, IIS controls the password for this account. Whether or not IIS controls the password affects the permissions the anonymous user has. When IIS controls the password, a sub authentication DLL (iissuba.dll) authenticates the user using a network logon. The function of this DLL is to validate the password supplied by IIS and to inform Windows that the password is valid, thereby authenticating the client. However, it does not actually provide a password to Windows. When IIS does not control the password, IIS calls the LogonUser() API in Windows and provides the account name, password and domain name to log on the user using a local logon. After the logon, IIS caches the security token and impersonates the account. A local logon makes it possible for the anonymous user to access network resources, whereas a network logon does not.
Basic Authentication
IIS Basic authentication as an implementation of the basic authentication scheme found in section 11 of the HTTP 1.0 specification.
As the specification makes clear, this method is, in and of itself, non-secure. The reason is that Basic authentication assumes a trusted connection between client and server. Thus, the username and password are transmitted in clear text. More specifically, they are transmitted using Base64 encoding, which is trivially easy to decode. This makes Basic authentication the wrong choice to use over a public network on its own.
Basic Authentication is a long-standing standard supported by nearly all browsers. It also imposes no special requirements on the server side -- users can authenticate against any NT domain, or even against accounts on the local machine. With SSL to shelter the security credentials while they are in transmission, you have an authentication solution that is both highly secure and quite flexible.
Digest Authentication
The Digest authentication option was added in Windows 2000 and IIS 5.0. Like Basic authentication, this is an implementation of a technique suggested by Web standards, namely RFC 2069 (superceded by RFC 2617).
Digest authentication also uses a challenge/response model, but it is much more secure than Basic authentication (when used without SSL). It achieves this greater security not by encrypting the secret (the password) before sending it, but rather by following a different design pattern -- one that does not require the client to transmit the password over the wire at all.
Instead of sending the password itself, the client transmits a one-way message digest (a checksum) of the user's password, using (by default) the MD5 algorithm. The server then fetches the password for that user from a Windows 2000 Domain Controller, reruns the checksum algorithm on it, and compares the two digests. If they match, the server knows that the client knows the correct password, even though the password itself was never sent. (If you have ever wondered what the default ISAPI filter "md5filt" that is installed with IIS 5.0 is used for, now you know.
Integrated Windows Authentication
Integrated Windows authentication (formerly known as NTLM authentication and Windows NT Challenge/Response authentication) can use either NTLM or Kerberos V5 authentication and only works with Internet Explorer 2.0 and later.
When Internet Explorer attempts to access a protected resource, IIS sends two WWW-Authenticate headers, Negotiate and NTLM.
If Internet Explorer recognizes the Negotiate header, it will choose it because it is listed first. When using Negotiate, the browser will return information for both NTLM and Kerberos. At the server, IIS will use Kerberos if both the client (Internet Explorer 5.0 and later) and server (IIS 5.0 and later) are running Windows 2000 and later, and both are members of the same domain or trusted domains. Otherwise, the server will default to using NTLM.
If Internet Explorer does not understand Negotiate, it will use NTLM.
So, which mechanism is used depends upon a negotiation between Internet Explorer and IIS.
When used in conjunction with Kerberos v5 authentication, IIS can delegate security credentials among computers running Windows 2000 and later that are trusted and configured for delegation. Delegation enables remote access of resources on behalf of the delegated user.
Integrated Windows authentication is the best authentication scheme in an intranet environment where users have Windows domain accounts, especially when using Kerberos. Integrated Windows authentication, like digest authentication, does not pass the user's password across the network. Instead, a hashed value is exchanged.
Client Certificate Mapping
A certificate is a digitally signed statement that contains information about an entity and the entity's public key, thus binding these two pieces of information together. A trusted organization (or entity) called a Certification Authority (CA) issues a certificate after the CA verifies that the entity is who it says it is. Certificates can contain different types of data. For example, an X.509 certificate includes the format of the certificate, the serial number of the certificate, the algorithm used to sign the certificate, the name of the CA that issued the certificate, the name and public key of the entity requesting the certificate, and the CA's signature. X.509 client certificates simplify authentication for larger user bases because they do not rely on a centralized account database. You can verify a certificate simply by examining the certificate.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vsent7/html/vxconIISAuthentication.asp
How to configure the sites in Web server (IIS)?
Advantages in IIS 6.0?
http://www.microsoft.com/windowsserver2003/iis/evaluation/features/default.mspx
http://www.microsoft.com/technet/treeview/default.asp?url=/technet/prodtechnol/windowsserver2003/proddocs/datacenter/gs_whatschanged.asp
IIS Isolation Levels?
Internet Information Server introduced the notion "Isolation Level", which is also present in IIS4 under a different name. IIS5 supports three isolation levels, that you can set from the Home Directory tab of the site's Properties dialog:
Low (IIS Process): ASP pages run in INetInfo.Exe, the main IIS process, therefore they are executed in-process. This is the fastest setting, and is the default under IIS4. The problem is that if ASP crashes, IIS crashes as well and must be restarted (IIS5 has a reliable restart feature that automatically restarts a server when a fatal error occurs).
Medium (Pooled): In this case ASP runs in a different process, which makes this setting more reliable: if ASP crashes IIS won't. All the ASP applications at the Medium isolation level share the same process, so you can have a web site running with just two processes (IIS and ASP process). IIS5 is the first Internet Information Server version that supports this setting, which is also the default setting when you create an IIS5 application. Note that an ASP application that runs at this level is run under COM+, so it's hosted in DLLHOST.EXE (and you can see this executable in the Task Manager).
High (Isolated): Each ASP application runs out-process in its own process space, therefore if an ASP application crashes, neither IIS nor any other ASP application will be affected. The downside is that you consume more memory and resources if the server hosts many ASP applications. Both IIS4 and IIS5 supports this setting: under IIS4 this process runs inside MTS.EXE, while under IIS5 it runs inside DLLHOST.EXE.
When selecting an isolation level for your ASP application, keep in mind that out-process settings - that is, Medium and High - are less efficient than in-process (Low). However, out-process communication has been vastly improved under IIS5, and in fact IIS5's Medium isolation level often deliver better results than IIS4's Low isolation. In practice, you shouldn't set the Low isolation level for an IIS5 application unless you really need to serve hundreds pages per second.
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