Interface (For Beginners)

• What is an interface?
• Where can we use an interface?

An interface contains only the signatures of methods, properties, events or indexers. A class or struct that implements the interface must implement the members of the interface that are specified in the interface definition.

A very nice article here: http://www.codeproject.com/Articles/18743/Interfaces-in-C-For-Beginners

Properties Of Interface:-

• Supports multiple inheritance (Single Class can implement multiple interfaces).

• Contains only incomplete method.

• Cannot Contains data members.

• By Default interface members is public (We Can not set any access modifier into interface members).

•  Interface cannot contain constructors.

    interface IApp

     {

           int Sum(int i, int j); //By Default Public

     }

     class App : IApp

     {

     // Can use either this way

        public int sum(int i, int j) //Must be declare Public

        {

           return i + j;

        }

    // Second method 
       int IApp.sum(int i, int j) //No need to declare Public

        {

           return i + j;

        }

     }