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);
   }
}


范例二

// keyword_delegate2.cs
// Calling both static and instance methods from delegates
using System;

// delegate declaration
delegate void MyDelegate();

public class MyClass 
{
   public void InstanceMethod() 
   {
      Console.WriteLine("A message from the instance method."); 
   }

   static public void StaticMethod() 
   {
      Console.WriteLine("A message from the static method.");
   }
}

public class MainClass 
{
   static public void Main() 
   {
      MyClass p = new MyClass();

      // Map the delegate to the instance method:
      MyDelegate d = new MyDelegate(p.InstanceMethod);
      d();

      // Map to the static method:
      d = new MyDelegate(MyClass.StaticMethod);
      d();
   }
}

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