1: using System;

   2: using System.Collections.Generic;

   3: using System.Linq;

   4: using System.Text;

   5:  

   6: namespace CSharp.Delegate

   7: {

   8:     //声明委托

   9:     public delegate void Del(string message);

  10:  

  11:     class Program

  12:     {

  13:         // Create a method for a delegate.

  14:         public static void DelegateMethod(string message)

  15:         {

  16:             System.Console.WriteLine(message);

  17:         }

  18:  

  19:         //定义回调方法

  20:         public static void MethodWithCallback(string message, Del callback)

  21:         {

  22:             callback(message);

  23:         }

  24:  

  25:         public static void Hello(string s)

  26:         {

  27:             System.Console.WriteLine("  Hello, {0}!", s);

  28:         }

  29:  

  30:         public static void Goodbye(string s)

  31:         {

  32:             System.Console.WriteLine("  Goodbye, {0}!", s);

  33:         }

  34:  

  35:         static void Main(string[] args)

  36:         {

  37:  

  38:             //new方法实例化委托，将方法作为参数进行传递

  39:             Del handler = new Del(DelegateMethod);

  40:             handler("向大家问个好吧。");

  41:             MethodWithCallback("大家好！", handler);

  42:  

  43:             //匿名方法来实例化委托 

  44:             Del anotherhandler = DelegateMethod;

  45:             anotherhandler("Hello World");

  46:             MethodWithCallback("I am coming!", anotherhandler);

  47:  

  48:             //“Lambda 表达式”是一个匿名函数,可以其表达式分配给委托类型

  49:             Del lamDel = (string s) =>

  50:             {

  51:                 Console.WriteLine(s);

  52:             };

  53:             lamDel("我是Lambda匿名委托！");

  54:  

  55:             //

  56:             //多路组合委托

  57:             //

  58:             //Hello,Goodbye,DelegateMethod 组合委托到d

  59:             Del d;

  60:             d = Hello;

  61:             d += Goodbye;

  62:             d += new Del(DelegateMethod);

  63:  

  64:             d("David");

  65:  

  66:             //移除委托DelegateMethod

  67:             d -= DelegateMethod;

  68:             d("David");

  69:  

  70:         }

  71:     }

  72: }

   1: class Mammals

   2: {

   3: }

   4:  

   5: class Dogs : Mammals

   6: {

   7: }

   8:  

   9: class Program

  10: {

  11:     // Define the delegate.

  12:     public delegate Mammals HandlerMethod();

  13:  

  14:     public static Mammals FirstHandler()

  15:     {

  16:         return null;

  17:     }

  18:  

  19:     public static Dogs SecondHandler()

  20:     {

  21:         return null;

  22:     }

  23:  

  24:     static void Main()

  25:     {

  26:         HandlerMethod handler1 = FirstHandler;

  27:  

  28:         // Covariance allows this delegate.

  29:         //    Mammals() <= Dogs ()  

  30:         //   Dogs  more drived types than Mammals

  31:         HandlerMethod handler2 = SecondHandler;

  32:  

  33:     }

  34: }

  35:  

   1: System.DateTime lastActivity;

   2: public Form1()

   3: {

   4:     InitializeComponent();

   5:  

   6: lastActivity = new System.DateTime();

   7: // KeyEventArgs <= System.EventArgs

   8: // MouseEventArgs <= System.EventArgs

   9: // System.EventArgs is less drived type than KeyEventArgs and

  10: // MouseEventArgs

  11:     this.textBox1.KeyDown += this.MultiHandler; //works with KeyEventArgs

  12: this.button1.MouseClick += this.MultiHandler; //works with MouseEventArgs

  13:  

  14: }

  15:  

  16: // Event hander for any event with an EventArgs or

  17: // derived class in the second parameter

  18: private void MultiHandler(object sender, System.EventArgs e)

  19: {

  20:     lastActivity = System.DateTime.Now;

  21: }