# 如何：合并委托（多路广播委托）（C# 编程指南） 本示例演示如何创建多播委托。 [委托](https://msdn.microsoft.com/zh-cn/library/900fyy8e.aspx)对象的一个有用属性是：可以使用 **+** 运算符将多个对象分配给一个委托实例。多播委托包含已分配委托的列表。在调用多播委托时，它会按顺序调用列表中的委托。只能合并相同类型的委托。 **-** 运算符可用于从多播委托中移除组件委托。 ``` 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! */ ``` ## 请参阅 [MulticastDelegate](https://msdn.microsoft.com/zh-cn/library/system.multicastdelegate.aspx) [C# 编程指南](https://msdn.microsoft.com/zh-cn/library/67ef8sbd.aspx) [事件（C# 编程指南）](https://msdn.microsoft.com/zh-cn/library/awbftdfh.aspx)