C#——如何合并委托（多播委托）

我不是女神ヾ 2023-01-03 04:22 96阅读 0赞

## C\#——如何合并委托（多播委托） ##

此示例演示如何创建多播委托。 委托对象的一个有用属性在于可通过使用 + 运算符将多个对象分配到一个委托实例。 多播委托包含已分配委托列表。 此多播委托被调用时会依次调用列表中的委托。 仅可合并类型相同的委托。

\-运算符可用于从多播委托中删除组件委托。

## 示例 ##

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)
        {
        
            Console.WriteLine($"  Hello, {s}!");
        }
    
        static void Goodbye(string s)
        {
        
            Console.WriteLine($"  Goodbye, {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!
    */