接口

接口，是一个约定，接口中有多个抽象方法，接口能实现多继承

实现了不相关类的，相同行为！

public interface IStringList

{

　　void Add(string s);//public abstract 不写出来，方法

　　int Count {get；}//public abstract 不写出来，属性

　　string this[int index] {get; set;}  //public abstract 不写出来，索引

}

如果不同接口，有同名的方法，为防止歧义，在方法名前加接口名，调用时只能用接口调用

(（IWindows) f  )  .Close();

using System;

interface Runner 
{ 
    void run();
}

interface Swimmer 
{ 
    void swim()
}

abstract class Animal  
{   
    abstract public void eat();
}  

class Person : Animal , Runner, Swimmer 
{
    public void run() 
    { 
        Console.WriteLine("run"); 
    }

    public void swim()  
    {
        Console.WriteLine("swim"); 
    }

    public override void eat() 
    { 
        Console.WriteLine("eat"); 
    }
    
    public void speak()
    {
        Console.WriteLine("speak"); 
    }
}

class TestInterface
{
    static void m1(Runner r) 
    { 
        r.run(); 
    }

    static void m2(Swimmer s) 
    { 
        s.swim(); 
    }

    static void m3(Animal a) 
    {
        a.eat(); 
    }

    static void m4(Person p)
    {
        p.speak();
    }

    public static void Main(string [] args)
    {
        Person p = new Person();
        m1(p);
        m2(p);
        m3(p);
        m4(p);

        Runner a = new Person();
        a.run();
    }
}

using System;

class InterfaceExplicitImpl
{
    static void Main()
    {   //1.
        FileViewer f = new FileViewer();
        f.Test();// 接口强转
        
        ( (IFileHandler) f ).Close();
        
        //2.
        IWindow w = new FileViewer();//接口引用
        w.Close();
        
        IFileHandler fh = new FileViewer();
        fh.Close();
    }
}

interface IWindow
{
    void Close();
}

interface IFileHandler
{
    void Close();
}

class FileViewer : IWindow, IFileHandler
{
    void IWindow.Close ()
    {
        Console.WriteLine( "Window Closed" );
    }

    void IFileHandler.Close()
    {
        Console.WriteLine( "File Closed" );
    }

    public void Test()
    {
        ( (IWindow) this ).Close();
    }
}