Shiva

Extension methods are methods added to an existing type without modifying it or deriving from it. These methods enable to extend the functionalty of existing types. They are implemented as static methods but are invoked as if they were instance methods on the extended type. For client code there is no difference between calling an extension method and the methods defined within the type.
To define and call the extension method
1. Define a static class to contain the extension method.
2. The class must be visible to client code (most probably a public class).
3. Include a static method in this class to implement the extension method.
4. The first parameter of this method specifies the type that the method is about to extend; it must be preceded with the "this" modifier.
5. In the calling code, add a using directive to specify the namespace that contains the extension method class.
6. Call the extension methods in the client code as if they were instance methods on the type.

.NET is the framework that can be used to develop various types of applications like Console, Desktop, Web, Services etc and ASP.NET is the web component part of the .NET framework which is used to develop Web applications. So a .NET developer is one who can work on any of these types of applications while ASP.NET developer is one who works on developing Web based applications like ASP.NET Web Forms, ASP.NET MVC, ASP.NET Web Services, ASP.NET Web APIs etc. But having said that ASP.NET developer should have the knowledge of .NET framework to work on ASP.NET.