C# 中的delegate

刚开始，见了多次，但是从来没有理解，一大早过来就先google一下，先把这个问题搞清楚。

delegate 的字面意思
vt. 委派…为代表
n. 代表

msdn上的解释
A delegate declaration defines a reference type that can be used to encapsulate a method with a specific signature. A delegate instance encapsulates a static or an instance method. Delegates are roughly similar to function pointers in C++; however, delegates are type-safe and secure.

delegate声明一种引用类型，用来封装有特定签名的方法，可以是一个静态的方法或是实例的方法。类似于C++中的方法指针。

声明格式

[attributes] [modifiers] delegate result-type identifier ([formal-parameters]);

范例一// keyword_delegate.cs
// delegate declaration
delegate void MyDelegate(int i);

class Program
{
   public static void Main()
   {
      TakesADelegate(new MyDelegate(DelegateFunction));
   }

   public static void TakesADelegate(MyDelegate SomeFunction)
   {
      SomeFunction(21);
   }
   
   public static void DelegateFunction(int i)
   {
      System.Console.WriteLine("Called by delegate with number: {0}.", i);
   }
}

 1 // keyword_delegate2.cs
 2 // Calling both static and instance methods from delegates
 3 using System;
 4 
 5 // delegate declaration
 6 delegate void MyDelegate();
 7 
 8 public class MyClass 
 9 {
10    public void InstanceMethod() 
11    {
12       Console.WriteLine("A message from the instance method."); 
13    }
14 
15    static public void StaticMethod() 
16    {
17       Console.WriteLine("A message from the static method.");
18    }
19 }
20 
21 public class MainClass 
22 {
23    static public void Main() 
24    {
25       MyClass p = new MyClass();
26 
27       // Map the delegate to the instance method:
28       MyDelegate d = new MyDelegate(p.InstanceMethod);
29       d();
30 
31       // Map to the static method:
32       d = new MyDelegate(MyClass.StaticMethod);
33       d();
34    }
35 }

本文中的大部分内容摘自http://msdn.microsoft.com/zh-cn/library/900fyy8e%28v=VS.71%29.aspx