Interfaces can be Inherited

One interface can inherit another. The syntax is the same as for inheriting classes. When a class implements an interface that inherits another interface, it must provide implementations for all the members defined within the interface inheritance chain. Following is an example:

 // One interface can inherit another. using System; public interface A {   void meth1();   void meth2(); } // B now includes meth1() and meth2() -- it adds meth3(). public interface B : A {   void meth3(); } // This class must implement all of A and B class MyClass : B {   public void meth1() {     Console.WriteLine("Implement meth1().");   }   public void meth2() {     Console.WriteLine("Implement meth2().");   }   public void meth3() {     Console.WriteLine("Implement meth3().");   } } class IFExtend {   public static void Main() {     MyClass ob = new MyClass();     ob.meth1();     ob.meth2();     ob.meth3();   } }

As an experiment you might want to try removing the implementation for meth1( ) in MyClass. This will cause a compile-time error. As stated earlier, any class that implements an interface must implement all methods defined by that interface, including any that are inherited from other interfaces.