如何：組合委派 (多點傳送委派) (C# 程式設計手冊)
本範例示範如何建立多點傳送委派。 delegate 物件具有的一種有用屬性，就是可使用 + 運算子將多個物件指派給一個委派執行個體。 多點傳送委派包含已指派委派的清單。 呼叫多點傳送委派時，它會依順序叫用清單中的委派。 只有相同型別的委派才能加以結合。
- 運算子可用來從多點傳送委派中移除某個元件委派。
範例
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)
{
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!
*/