委托的使用和合并

 

delegate void Del(string s);

class TestClass
{
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()
{
Del a, b, c, d;

// Create the delegate object a that references
// the method Hello:
a = Hello;

// Create the delegate object b that references
// the method Goodbye:
b = Goodbye;

// The two delegates, a and b, are composed to form c:
c = a + b;

// Remove a from the composed delegate, leaving d,
// which calls only the method Goodbye:
d = c - a;

System.Console.WriteLine("Invoking delegate a:");
a("A");
System.Console.WriteLine("Invoking delegate b:");
b("B");
System.Console.WriteLine("Invoking delegate c:");
c("C");
System.Console.WriteLine("Invoking delegate d:");
d("D");
}
}

输出结果

Invoking delegate a:
  Hello, A!
Invoking delegate b:
  Goodbye, B!
Invoking delegate c:
  Hello, C!
  Goodbye, C!
Invoking delegate d:
  Goodbye, D!

如果方法委托里的方法有返回值，则返回最后一个有返回值的方法的返回值，