Interface in C#

Interface

* We create a interfaces using interface keyword. Just like classes interfaces also contains properties, methods, delegates or events, but only declarations and no implementations.

 It is a compile time error to provide implementations for any interface member.

* Interface members are public by default, and they don't allow explicit access modifiers.

 Interfaces cannot contain fields.

* If a class or a struct inherits from an interface, it must provide implementation for all interface members. Otherwise, we get a compiler error.

A class or a struct can inherit from more than one interface at the same time, but where as, a class cannot inherit from more than once class at the same time.

* Interfaces can inherit from other interfaces. A class that inherits this interface must provide implementation for all interface members in the entire interface inheritance chain.

We cannot create a instance of an interface, but an interface reference variable can point to a derived class object.

Interface Naming convention. Interface names are prefixed with capital!

Interface Sample program:

namespace @interface
{
    //Interface is only for method declaration not implementation.
    interface ICustomer
    {
        void Print();
    }
    class Customer : ICustomer
    {
        public void Print()
        {
            Console.WriteLine("Interface print method");
            Console.ReadLine();
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            Customer c1 = new Customer();
            c1.Print();
        }
    }

}