How can a C# anonymous class implement an interface?

Anonymous types can implement interfaces via a dynamic proxy. Check out http://wblo.gs/feE  and https://github.com/jcbowers/DuckTyping

This is called Dynamic Binding...
when the reference id of child class put into the reference variable of parent class or Interface .then this concept is called Dynamic Binding.

ITest InterfaceWithoutObject = new Test();
//parent                                       // Child class

Although you can't instantiate an interface, you can declare variables, parameters or method return types of an interface type.

You can then assign instances of classes or structs which implement the interface to the variable, parameter or return value and invoke interface methods/properties using that variable etc.

The advantage of this is that it enables you to write generic code which applies to any type which implements an interface even if those types otherwise have no relation to each other.

Thanks for the reply. There is a mistake in my question as it should be How anonymous class can instantiate an interface.You are saying that InterfaceWithoutObject is initialized by assigning a new Test object to it as:

 ITest InterfaceWithoutObject = new Test();

I'm little confused as ITest is actually an interface and is getting instantiated by Test(). A general rule is we cannot create an object of interface but this code builds successfully. I did a little googling and found that we can instantiate an interface using anonymous class. Could you explain more?

Well, the named class Test is implementing the ITest interface and is therefore providing an implementation of its display() method.

This class also has a private instance field, InterfaceWithoutObject, of type ITest and is initialized by assigning a new Test object to it.

However, whilst the code compiles, if you try to run it and include a line such as this:

   Test t = new Test();

then you'll find that execution ends with a StackOverflowException.

This is because the code creates an infinite loop - when a Test object is created, the private field is initialized creating another Test object, and so on until the stack overflows.

BTW, you're right that an anonymous type can't implement any interfaces.