Interface is a type. Its purpose is to make plug-n-play component e.g. USB on laptop. Now many things can be connected on this USB place.

For polymorphism, interfaces are also used. This is also called Run-time polymorphism.

The name of built-in interfaces starts with “I”. In interface, there is only declaration but no definition.

    interface MyFirstApplicationInterface
	    int LogId{get;set;}
	    void Save();
	    void Cancel();

Note that in interface, we cannot write anything in get and set methods like in LogId property.

If we implement 2 interfaces which have 1 method with same name then to implement this method, we would have to mention InterfaceA.Save() to implement InterfaceA’s Save method. For example,

    public class MyClass: InterfaceA, InterfaceB
	    public void InterfaceA.Save()