Interview Questions on C#, C Sharp and Answers

9/02/2009 No Comment
1. 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.

2. 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",

3. What are the new features of Framework 1.1?
1. Native Support for Developing Mobile Web Applications
2. 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.

3. 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.

4. Native Support for Communicating with ODBC and Oracle Databases

5. 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.

6. 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.

4. 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.

• Execute Reader - basically, this method returns a Data Reader which is filled with the data that is retrieved using the command. This is known as a forward-only retrieval of records - it uses your sql statement to read through the table from the first to the last.
There are many Data Reader examples on this site. Just go to and choose Data Reader from the Dropdown List
Usage: cmd.ExecuteReader
• ExecuteNonQuery - this method returns no data at all. It is used mainly with Inserts and Updates of tables.
Here, also, we have many code samples using ExecuteNonQuery.
Inserting records
Updating a Record
Useage: cmd.ExecuteNonQuery
• ExecuteScalar - Returns only one value after executing the query - it returns the first field in the first row. This is very light-weight and is perfect when all your query asks for is one item.
This would be excellent for receiving a count of records (Select Count(*)) in an sql statement, or for any query where only one specific field in one column is needed.
1 different types of session

Tracking using Session Objects, URL-Rewriting and Hidden Fields i.e. either using
A hidden field in the html or using Page.RegisterHiddenField (in 2003), but in 2005, it has been depreciated, and it is Client.RegisterHiddenField(Key, Value)

2 types of datasets
To the best of my knowledge there is only 1 dataset. But there are various data sources. So I wonder whether you are asking me what the different Data Sources are. If so here they are
• ObjectDataSource
• SqlDataSource
• AccessDataSource
• XmlDataSource
• SiteMapDataSource

3 How can I use a dll in a machine, which is in a network, in my proj which is in some other machine?
Make the other machine a COM+ server and deploy the dll under the COM+ interop services. So that you could use it as a DCOM component.

4 what i have to do if I need a component to b shared my multiple application, say one is a web and other a windows
I think by making it a dll and then using its reference by copying the dll in to the projects bin directory. I think I would have to research a little bit on this. I will do that I would let you know about it. Usually for web we use Web Control , and windows we use windows control, to create our own custom control.

5 how to create 2 virtual directories with same port no: say 80
Why not, you can create ‘n’ numbers of virtual Directories under a Web Site, but the alias name should be different

6 Types of polymorphism
Compile time (function Overloading) and Run time Polymorphism (function Overriding)

7 Purpose of shared assembly
A shared assembly is one that can be referenced by more than one application. In order to share an assembly, the assembly must be explicitly built for this purpose by giving it a cryptographically strong name. Using the Sn.exe command from the command prompt. If we want to create an assembly which needs to be referenced by the same application and no other application, then it should be a private assembly.

8 How can you make your application to work in a newer version of .net frame work
By removing all unused variables, since 2005 wont support the usage of unused variables. Then by removing all the depreciated functions like the one I have mentioned against your Qn1. These are the couple of ways by which you could make your appln work n newer version. There may be other stuffs also, but these generally what I have experienced in 2005 , when compared to 2003, if I come to know about other features I would let you know for sure.

9. What is MSIL, IL?
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.

10. 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 Main() {
ldstr "Hello, IL!"
call void System.Console::WriteLine(class System.Object)
Just put this into a file called, and then run ilasm An exe assembly will be generated.

11.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.

12. 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.

13. 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.

14. 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

15. 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.
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