An interface contains only the signatures of methods, delegates or events. An interface looks like a class, but has no implementation. The only thing it contains is declarations of events, indexers, methods and/or properties. Interfaces in C # provide a way to achieve runtime polymorphism.

Why Use Interfaces?

To allows a class to inherit multiple behaviors from multiple interfaces.

To avoid name ambiguity between the methods of the different classes as was in the use of multiple inheritances in C++.

To combine two or more interfaces such that a class need only implement the combined result. The example code for this is provided as a source file to be downloaded.

To allows Name hiding: Name hiding is the ability to hide an inherited member name from any code outside the derived class.

Defining an Interface

interface IMyInterface
{
void MethodToImplement();
}

Implementation of Interface

class InterfaceImplementer : IMyInterface
{
static void Main()
{
InterfaceImplementer iImp = new InterfaceImplementer();
iImp.MethodToImplement();
}

public void MethodToImplement()
{
Console.WriteLine("MethodToImplement() called.");
}
}

Compile example:

Output: