c#中观查者模式实现（委托版）_c# 实现查询模式-优快云博客

本文介绍了一种基于C#的观察者模式实现方法，通过委托和事件来通知多个观察者对象更新状态。示例中使用银行账户取款事件触发邮件通知作为应用场景。

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using System;
using System.Collections.Generic;
using System.Text;
namespace ObserverDemo
{
    class 观查者模式委托版
    {
        public static void Main(string[] args)
        {
            BankAccount count = new BankAccount();
            count.WithDrawEvent += new BankAccount.WithDrawEventHandler( new Email().Update);
            count.WithDraw(50);
            Console.Read();
        }
    }
    abstract class ISubject
    {
        public delegate void WithDrawEventHandler(object sender, UserMsgInfoEventArgs args);
        public event WithDrawEventHandler WithDrawEvent;
        public void OnWithDrawEvent(UserMsgInfoEventArgs args)
        {
            if (this.WithDrawEvent != null)
            {
                this.WithDrawEvent(this, args);
            }
        }
    }
    class BankAccount : ISubject
    {
        public int money = 90 ;        
        
        public void WithDraw( int money )
        {
            this.money -= money;
            OnWithDrawEvent(new UserMsgInfoEventArgs(string.Format("取走{0}钱,还有{1}钱", money, this.money)));
        }
    }
    class UserMsgInfoEventArgs : EventArgs
    {
        //传送信息 
        public string sendinfo;
        public UserMsgInfoEventArgs(string info)
        {
            this.sendinfo = info;
        }
    }
    class Email
    {
        public void Update(object sender, UserMsgInfoEventArgs args)
        {
            Console.WriteLine( args.sendinfo );
        }
    }
}