观察者模式 C#

用C#实现观察者模式：用委托和事件

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication3
{
    public class Cat
    {
        private string name;
        public string Name
        {
            get { return name; }
        }
        public delegate void CatShoutEventHandler(Object sender,CatShoutEventArgs args); //声明委托
        public event CatShoutEventHandler CatShout; //声明事件
        public Cat(string name)
        {
            this.name = name;
        }
        //事件参数
        public class CatShoutEventArgs : EventArgs
        {
            private  string sound;
            public string Sound
            {
                get { return sound;}
            }
            public CatShoutEventArgs(string sound)
            {
                this.sound = sound;
            }
        }

        protected virtual void OnShout(CatShoutEventArgs e)
        {
            if (CatShout != null)
            {
                CatShout(this,e);
            }
        }

        public void shout()
        {
            if (this.Name == "jack")
            {
                CatShoutEventArgs e = new CatShoutEventArgs("large sound");
                OnShout(e);
            }
        }

    }
    public class Mouse
    {
        private string name;
        public string Name
        {
            get { return name;}
        }
        public Mouse(){
        }
        public Mouse(string name) {
            this.name = name;
        }
        public static void ShowMsg(Object sender, Cat.CatShoutEventArgs e)
        {   //静态方法
            Cat cat = (Cat)sender;
            Console.WriteLine("有只猫，它的名字是：{0} 没有名字 快跑: ", cat.Name);
            Console.WriteLine("它的声音:"+e.Sound);
            Console.WriteLine();
        }

        public  void ShowMsgWithName(Object sender, Cat.CatShoutEventArgs e)
        {  
　　　　　　 Cat cat = (Cat)sender;
            Console.WriteLine("有只猫，它的名字是：{0} 小老鼠{1} 快跑: ", cat.Name,this.Name);
            Console.WriteLine("它的声音:" + e.Sound);
            Console.WriteLine();
        }

    }
    class Program
    {
        static void Main()
        {
            Cat cat= new Cat("jack");
            Mouse mouse = new Mouse("jim");

            cat.CatShout += Mouse.ShowMsg;  //注册静态方法
            cat.CatShout += (new Mouse("tom")).ShowMsgWithName;  //给匿名对象注册方法
            cat.CatShout += new Cat.CatShoutEventHandler(mouse.ShowMsgWithName);
            cat.shout();   //猫叫，会自动调用注册过对象的方法
            Console.ReadLine();
        }
    }

}

输出：
有只猫，它的名字是：jack 没有名字 快跑:
它的声音:large sound
有只猫，它的名字是：jack 小老鼠tom 快跑:
它的声音:large sound
有只猫，它的名字是：jack 小老鼠jim 快跑:
它的声音:large sound