C # Grammar Exercises (15): interface

Interfaces are declared, not implemented, and cannot be instantiated;

Interfaces can contain methods, properties, events, indexers, but no fields;

Interface members are implicitly public and do not use an access modifier;

Classes, structs, and interfaces can inherit multiple interfaces;

A class that inherits an interface must implement an interface member, unless it is an abstract class;

The interface member implemented by a class must be public and non-static.

Getting Started Sample:

using System;

interface MyInterface
{
　　 int Sqr(int x);
}

class MyClass : MyInterface
{
　　 public int Sqr(int x) { return x * x; }
}

class Program
{
　　 static void Main()
　　 {
　　　　 MyClass obj = new MyClass();
　　　　 Console.WriteLine(obj.Sqr(3)); // 9

　　　　 MyInterface intf = new MyClass();
　　　　 Console.WriteLine(intf.Sqr(3));

　　　　 Console.ReadKey();
　　 }
}