Can any one explain the interfaces in C#.net in details?

Interfaces are basically abstract classes: they contain only the "structure" of a specific kind of classes. For example: if you use wpf, you will surely have encountered IValueConverter. This is an interface you MUST implement in your class in order to make wpf use that class to convert values because it needs specific methods. Think an interface as a base class, but you cannot access the base code (because it actually does not exist) and you MUST write your own version of each method.

The advantages of the interfaces come in when you are instantiating a class of a generic type, but with a specific use. For example let's suppose you have the interface IShape. Classes Hexagon, Square and circle implement it. Now you need to write a method which outputs the area of a shape. The IShape interface contains the method GetArea and, as the above cited classes implement IShape, the developer has written a GetArea method for each one. Now what you have to do is simply write a method and ask a reference to an IShape in its parameters and then call IShape.GetArea and, based on what you pass inside that method (which could be either an Hexagon, Square or Circle instance, but not any other object which does not implement IShape) the program will call the corresponding GetArea method.

I hope this helped even if it is not so clear: interfaces are not so easy to learn (well, as far as I am concerned, I took some time to understand inheritance and I have got to understand interfaces later because I was not able to tell them apart from abstract classes. I realised later that they were almost exactly the same thing).

Edit: there actually is a difference between an abstract class and an interface. Look this: http://stackoverflow.com/questions/1913098/what-is-the-difference-between-an-interface-and-abstract-class

LG

Probably many could, but why? Why would you think that a Quick Answer written specially for you should be better than many articles and books written thoroughly? Don't you think you should better read some of available literature?
—SA