delegate (C# Reference)

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最新推荐文章于 2024-08-12 15:32:33 发布

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原文链接：http://www.cnblogs.com/sandy_liao/archive/2010/11/29/1891503.html

本文介绍了委托类型的声明形式，指出委托关键字用于声明可封装命名或匿名方法的引用类型，它类似C++函数指针但更安全，是事件的基础。还说明了委托可通过命名或匿名方法实例化，以及两种实例化方式的相关信息。

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The declaration of a delegate type takes the following form:

Copy

public delegate void TestDelegate(string message);

The delegate keyword is used to declare a reference type that can be used to encapsulate a named or an anonymous method. Delegates are similar to function pointers in C++; however, delegates are type-safe and secure. For applications of delegates, see Delegates and Generic Delegates.

Remarks

Delegates are the basis for Events.

A delegate can be instantiated by associating it either with a named or anonymous method. For more information, see Named Methods and Anonymous Methods.

For use with named methods, the delegate must be instantiated with a method that has an acceptable signature. For more information on the degree of variance that is allowed in the method signature, see Covariance and Contravariance in Delegates. For use with anonymous methods, the delegate and the code to be associated with it are declared together. Both ways of instantiating delegates are discussed in this section.

代码

using System;
// Declare delegate -- defines required signature:
delegate void SampleDelegate( string message);

class MainClass
{
     // Regular method that matches signature:
     static void SampleDelegateMethod( string message)
    {
        Console.WriteLine(message);
    }

     static void Main()
    {
         // Instantiate delegate with named method:
        SampleDelegate d1 = SampleDelegateMethod;
         // Instantiate delegate with anonymous method:
        SampleDelegate d2 = delegate ( string message)
        {
            Console.WriteLine(message);
        };

         // Invoke delegate d1:
        d1( " Hello " );
         // Invoke delegate d2:
        d2( " World " );
    }
}

转载于:https://www.cnblogs.com/sandy_liao/archive/2010/11/29/1891503.html