C# Interview Questions

Part II

1) 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.

2) 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.

3)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

4)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.

<httpModules>
<remove name=”Session” />
</httpModules>

5)What is main difference between Global.asax and Web.Config?

ASP.NET uses the global.asax to establish any global objects that your Web application uses. The .asax extension denotes an application file rather than .aspx for a page file. Each ASP.NET application can contain at most one global.asax file. The file is compiled on the first page hit to your Web application. ASP.NET is also configured so that any attempts to browse to the global.asax page directly are rejected. However, you can specify application-wide settings in the web.config file. The web.config is an XML-formatted text file that resides in the Web site’s root directory. Through Web.config you can specify settings like custom 404 error pages, authentication and authorization settings for the Web site, compilation options for the ASP.NET Web pages, if tracing should be enabled, etc.

6) What’s the implicit name of the parameter that gets passed into the class’ set method?

 Value, and it’s datatype depends on whatever variable we’re changing.

7) How do you inherit from a class in C#?

Place a colon and then the name of the base class.

8) Does C# support multiple inheritance?

No, use interfaces instead.

9) When you inherit a protected class-level variable, who is it available to?

Classes in the same namespace.

10) Are private class-level variables inherited?

Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited. But they are.

11) Describe the accessibility modifier protected internal.

 It’s available to derived classes and classes within the same Assembly (and naturally from the base class it’s declared in).

12) C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write?

Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there’s no implementation in it.

13) What’s the top .NET class that everything is derived from?

System.Object.

14) How’s method overriding different from overloading?

When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.

15) What does the keyword virtual mean in the method definition?

 The method can be over-ridden.

16) Can you declare the override method static while the original method is non-static?

No, you can’t, the signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.

17) Can you override private virtual methods?

No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.

18) Can you prevent your class from being inherited and becoming a base class for some other classes?

Yes, that’s what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It’s the same concept as final class in Java.

19) Can you allow class to be inherited, but prevent the method from being over-ridden?

Yes, just leave the class public and make the method sealed.

20) What’s an abstract class?

A class that cannot be instantiated. A concept in C++ known as pure virtual method. A class that must be inherited and have the methods over-ridden. Essentially, it’s a blueprint for a class without any implementation.

21) When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)?

 When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.

22) What’s an interface class?

 It’s an abstract class with public abstract methods all of which must be implemented in the inherited classes.

23) Why can’t you specify the accessibility modifier for methods inside the interface?

They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it’s public by default.

24) Can you inherit multiple interfaces?

Yes, why not.

25) And if they have conflicting method names?

It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.