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delegate

  delegate定义了一个函数引用类型,犹如C++中的typedef,也犹如Objc中的Block(在捕获变量上有点差异)。

  1、有名方法,delegate捕获的方法可以是实例方法或静态方法。

 1 // Declare a delegate
 2 delegate void Del();
 3 
 4 class SampleClass
 5 {
 6     public void InstanceMethod()
 7     {
 8         System.Console.WriteLine("A message from the instance method.");
 9     }
10 
11     static public void StaticMethod()
12     {
13         System.Console.WriteLine("A message from the static method.");
14     }
15 }
16 
17 class TestSampleClass
18 {
19     static void Main()
20     {
21         SampleClass sc = new SampleClass();
22 
23         // Map the delegate to the instance method:
24         Del d = sc.InstanceMethod;
25         d();
26 
27         // Map to the static method:
28         d = SampleClass.StaticMethod;
29         d();
30     }
31 }
32 /* Output:
33     A message from the instance method.
34     A message from the static method.
35 */
View Code

  2、匿名方法。

  

  也可以不创建delegate对象:

  

  对于捕获,编译器会创建额外的类来容纳变量,而之前定义该变量的类的实例拥有该变量的引用,捕获到该变量的匿名方法同样也拥有该变量的引用。所以,方法内的变量并不是我们想象中存储在方法对应的栈帧中。我们知道,所有引用都是在拥有该引用的实例的堆上,除非委托被回收,否则该引用就不会被销毁。

合并委托

  可以将多个委托对象相加得到一个单一个组合委托对象(合并委托)。

using System;

// Define a custom delegate that has a string parameter and returns void.
delegate void CustomDel(string s);

class TestClass
{
    // Define two methods that have the same signature as CustomDel.
    static void Hello(string s)
    {
        System.Console.WriteLine("  Hello, {0}!", s);
    }

    static void Goodbye(string s)
    {
        System.Console.WriteLine("  Goodbye, {0}!", s);
    }

    static void Main()
    {
        // Declare instances of the custom delegate.
        CustomDel hiDel, byeDel, multiDel, multiMinusHiDel;

        // In this example, you can omit the custom delegate if you 
        // want to and use Action<string> instead.
        //Action<string> hiDel, byeDel, multiDel, multiMinusHiDel;

        // Create the delegate object hiDel that references the
        // method Hello.
        hiDel = Hello;

        // Create the delegate object byeDel that references the
        // method Goodbye.
        byeDel = Goodbye;

        // The two delegates, hiDel and byeDel, are combined to 
        // form multiDel. 
        multiDel = hiDel + byeDel;

        // Remove hiDel from the multicast delegate, leaving byeDel,
        // which calls only the method Goodbye.
        multiMinusHiDel = multiDel - hiDel;

        Console.WriteLine("Invoking delegate hiDel:");
        hiDel("A");
        Console.WriteLine("Invoking delegate byeDel:");
        byeDel("B");
        Console.WriteLine("Invoking delegate multiDel:");
        multiDel("C");
        Console.WriteLine("Invoking delegate multiMinusHiDel:");
        multiMinusHiDel("D");
    }
}
/* Output:
Invoking delegate hiDel:
  Hello, A!
Invoking delegate byeDel:
  Goodbye, B!
Invoking delegate multiDel:
  Hello, C!
  Goodbye, C!
Invoking delegate multiMinusHiDel:
  Goodbye, D!
*/
View Code

 

参考:

1、http://msdn.microsoft.com/zh-cn/library/98dc08ac(v=vs.90).aspx

2、http://msdn.microsoft.com/zh-cn/library/0yw3tz5k(v=vs.90).aspx

3、http://www.cnblogs.com/wenjiang/archive/2013/03/12/2954913.html

4、http://msdn.microsoft.com/zh-cn/library/ms173175.aspx

posted on 2014-06-25 15:28  Tekkaman  阅读(371)  评论(0编辑  收藏  举报