C#语言知识点整理-事件

   1:  

   2: using System;

   3: using System.Collections.Generic;

   4: using System.Linq;

   5: using System.Text;

   6:  

   7: namespace CSharp.Event

   8: {

   9:     public delegate void MyEventHandler(string s);

  10:  

  11:     public interface IPublisher

  12:     {

  13:         // 接口可声明事件。

  14:         event EventHandler RaiseCustomEvent;

  15:         //自定义事件访问器，可选

  16:         event MyEventHandler OnMyEvent;

  17:     }

  18:  

  19:     /// 

  20:     /// 自定义EventArgs类，用来保存事件信息

  21:     /// 

  22:     public class CustomEventArgs : EventArgs

  23:     {

  24:         private string message;

  25:  

  26:         public string Message

  27:         {

  28:             get { return message; }

  29:             set { message = value; }

  30:         }

  31:  

  32:         public CustomEventArgs(string s)

  33:         {

  34:             message = s;

  35:         }

  36:  

  37:     }

  38:  

  39:     /// 

  40:     /// 发布者

  41:     /// 

  42:     class Publisher : IPublisher

  43:     {

  44:         object objectLock = new Object();

  45:         //使用EventHandler 声明事件

  46:         public event EventHandler RaiseCustomEvent;

  47:         private event MyEventHandler _myEventHandler;

  48:  

  49:         /// 

  50:         ///  在大多数情况下都不需要提供自定义的事件访问器。

  51:         ///  如果您在代码中没有提供自定义的事件访问器，编译器会自动添加事件访问器。

  52:         /// 

  53:         public event MyEventHandler OnMyEvent

  54:         {

  55:             add

  56:             {

  57:                 lock (objectLock)

  58:                 {

  59:                     _myEventHandler += value;

  60:                 }

  61:             }

  62:             remove

  63:             {

  64:                 lock (objectLock)

  65:                 {

  66:                     _myEventHandler -= value;

  67:                 }

  68:             }

  69:         }

  70:  

  71:         public void DoSomething()

  72:         {

  73:             //省略。。。

  74:  

  75:             //自己引发事件

  76:             OnRaiseCustomEvent(new CustomEventArgs("Did something"));

  77:             //省略。。。

  78:  

  79:             if (_myEventHandler != null)

  80:             {

  81:  

  82:                 _myEventHandler("你轻轻的走，不带走一片云彩！");

  83:             }

  84:  

  85:         }

  86:  

  87:         /// 

  88:         /// 公开protected virtual方法，允许继承类重写事件调用行为

  89:         /// 

  90:         /// 

  91:         protected virtual void OnRaiseCustomEvent(CustomEventArgs e)

  92:         {

  93:             EventHandler handler = RaiseCustomEvent;

  94:  

  95:             //如果没有订阅者，事件为空

  96:             if (handler != null)

  97:             {

  98:                 e.Message += String.Format(" at {0}", DateTime.Now.ToString());

  99:  

 100:                 //触发事件

 101:                 handler(this, e);

 102:             }

 103:         }

 104:  

 105:    

 106:     }

 107:  

 108:     /// 

 109:     /// 订阅者

 110:     /// 

 111:     class Subscriber

 112:     {

 113:         private string id;

 114:         public Subscriber(string ID, Publisher pub)

 115:         {

 116:             id = ID;

 117:             //多路广播委托实现事件订阅

 118:             pub.RaiseCustomEvent += HandleCustomEvent;

 119:             pub.OnMyEvent += new MyEventHandler(pub_OnMyEvent);

 120:         }

 121:  

 122:         void pub_OnMyEvent(string s)

 123:         {

 124:             Console.WriteLine(string.Format("{0} 的开场白：{1}", id, s));

 125:         }

 126:  

 127:         /// 

 128:         /// 当订阅者接收到事件，该做什么反应

 129:         /// 也就是常说的事件处理逻辑

 130:         /// 

 131:         /// 

 132:         /// 

 133:         void HandleCustomEvent(object sender, CustomEventArgs e)

 134:         {

 135:             Console.WriteLine(id + " received this message: {0}", e.Message);

 136:         }

 137:     }

 138:  

 139:     class Program

 140:     {

 141:         static void Main(string[] args)

 142:         {

 143:             //实例一个发布者

 144:             Publisher pub = new Publisher();

 145:             //实例两个订阅者sub1,sub2,他们计划收听pub

 146:             Subscriber sub1 = new Subscriber("sub1", pub);

 147:             Subscriber sub2 = new Subscriber("sub2", pub);

 148:  

 149:             //发布者通过DoSomething触发事件，开始发布信息

 150:             pub.DoSomething();

 151:  

 152:             Console.WriteLine("Press Enter to close this window.");

 153:             Console.ReadLine();

 154:         }

 155:     }

 156: }