Delegate, Method as Parameter.

1. 代理, 将方法作为另一方法的参数. 类似C里面的函数指针.
   

   using System;
   using System.Windows.Forms;
   using System.Threading;
   
   namespace Demo
   {
       public delegate void Greeting(string name);
   
       public class Demo
       {
           private static void GreetingEnglish(string name)
           {
               Console.WriteLine ("Hello,{0}", name);
           }
           private static void GreetingChinese(string name)
           {
               Console.WriteLine ("你好,{0}", name);
           }
           //委托,将方法作为另一方法的参数.委托可以代表一系列返回值和参数类型与其一致的方法.
           private static void GreetingPeople(string name, Greeting greet)
           {
               greet (name);
           }
               
           public static void Main()
           {
               GreetingPeople ("Jeffrey Richter", GreetingEnglish);
               GreetingPeople ("刘德华", GreetingChinese);
               Console.ReadKey ();
           }
       }
   
   }

2. 将方法绑定到委托
   

   using System;
   using System.Threading;
   
   namespace Demo
   {
       public delegate void Greeting(string name);
   
       public class Demo
       {
           private static void GreetingEnglish(string name)
           {
               Console.WriteLine ("Hello,{0}", name);
           }
           private static void GreetingChinese(string name)
           {
               Console.WriteLine ("你好,{0}", name);
           }
           private static void GreetingFrance(string nom)
           {
               Console.WriteLine ("Bonjour,{0}", nom);
           }
           //delegate: use the Method name as Parameters.
           private static void GreetingPeople(string name, Greeting greet)
           {
               greet (name);
           }
               
           public static void Main()
           {
               GreetingPeople ("Jeffrey Richter", GreetingEnglish);
               GreetingPeople ("刘德华", GreetingChinese);
               //bind Method to Delegate
               Greeting chinese = GreetingChinese;
               Greeting english = GreetingEnglish;
               english += GreetingFrance;
               chinese ("许明会");
               english ("Matt Petrek");
               Console.ReadKey ();
           }
       }
   }

3. 委托与接口
   

   using System;
   using System.Threading;
   
   namespace Demo
   {
       interface IGreeting{
           void Greeting(string name);
       };
   
       public class GreetingChinese:IGreeting
       {
           public void Greeting(string name)
           {
               Console.WriteLine ("你好，{0}", name);
           }
       }    
       public class GreetingEnglish:IGreeting
       {
           public void Greeting(string name)
           {
               Console.WriteLine ("Hello,{0}", name);
           }
       }
       public class Demo
       {
           private static void Greeting(string name, IGreeting greeting)
           {
               greeting.Greeting (name);
           }
           public static void Main()
           {
               IGreeting chinese = new GreetingChinese ();
               IGreeting english = new GreetingEnglish ();
               chinese.Greeting ("许明会");
               english.Greeting ("Jeffrey Richter");
               Greeting ("Matt Petrik", english);
               Console.ReadKey ();
           }
       }
   }

4. 更好的封装，事件的由来
   

   using System;
   using System.Threading;
   
   namespace Demo
   {
       public delegate void Greet(string name);
   
       public class GreetingManager
       {
           public Greet deleGreet;
           public void Greeting(string name, Greet greet)
           {
               greet (name);
           }
       }
   
       public class Demo
       {
           private static void GreetingEnglish(string name)
           {
               Console.WriteLine ("Hello,{0}", name);
           }
           private static void GreetingChinese(string name)
           {
               Console.WriteLine ("你好,{0}", name);
           }
   
           //Main()
           public static void Main()
           {
               GreetingManager gm = new GreetingManager ();
               gm.deleGreet = GreetingChinese;
               gm.deleGreet += GreetingEnglish ;
               gm.Greeting ("Matt Petrik",gm.deleGreet);
               Console.ReadKey ();
           }
       }
   }

5. 更好的封装，准备引入事件
   

   using System;
   using System.Threading;
   
   namespace Demo
   {
       public delegate void Greet(string name);
   
       public class GreetingManager
       {
           public Greet deleGreet;
   
           public void Greeting(string name)
           {
               if (deleGreet!=null) {
                   deleGreet(name);
               }
           }
       }
   
       public class Demo
       {
           private static void GreetingEnglish(string name)
           {
               Console.WriteLine ("Hello,{0}", name);
           }
           private static void GreetingChinese(string name)
           {
               Console.WriteLine ("你好,{0}", name);
           }
   
           //Main()
           public static void Main()
           {
               GreetingManager gm = new GreetingManager ();
               gm.deleGreet = GreetingChinese;
               gm.deleGreet += GreetingEnglish ;
               gm.Greeting ("Matt Petrik");
               Console.ReadKey ();
           }
       }
   }

6. 委托的目的是把它暴露到外面，以让客户端进行方法注册。Event保证在类的内部总是Private，可认为是为Delegate定制的Property。
   

   using System;
   using System.Threading;
   
   namespace Demo
   {
       public delegate void Greet(string name);
   
       public class GreetingManager
       {
           //public Greet deleGreet;
           public event Greet EventGreet;
   
           public void Greeting(string name)
           {
               if (EventGreet!=null) 
                   EventGreet(name);
           }
       }
   
       public class Demo
       {
           private static void GreetingEnglish(string name)
           {
               Console.WriteLine ("Hello,{0}", name);
           }
           private static void GreetingChinese(string name)
           {
               Console.WriteLine ("你好,{0}", name);
           }
   
           //Main()
           public static void Main()
           {
               GreetingManager gm = new GreetingManager ();
               gm.EventGreet += GreetingChinese;
               gm.EventGreet += GreetingEnglish ;
               //Greeting call from client, that's not good!
               gm.Greeting ("Matt Petrik");
               Console.ReadKey ();
           }
       }
   }

7. .NET框架的委托和事件
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