C#_delegate - 有返回值手工调用

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;

namespace EventClock
{

    public class ClassWithDelegate
    {
        //封装了一个返回值为int的多重委托方法
        public delegate int DelegateThatReturns();
        public DelegateThatReturns theDelegate;

        public void Run()
        {
            for (; ; )
            {
                Thread.Sleep(500);

                if (theDelegate != null)
                {
                    //显式调用每个委托方法
                    foreach (DelegateThatReturns del in theDelegate.GetInvocationList())
                    {
                        int result = del();
                        Console.WriteLine("Delegates fired! return result: {0}",result);
                    }
                    Console.WriteLine();
                }
            }
        }
    }

    public class FirstSubscribe
    {
        private int myCounter = 0;

        public void Subscribe(ClassWithDelegate theClassWithDelegate)
        {
            theClassWithDelegate.theDelegate += new ClassWithDelegate.DelegateThatReturns(DisplayCounter);
        }

        public int DisplayCounter()
        {
            return ++myCounter;
        }
    }
    public class SecondSubscribe
    {
        private int myCounter = 0;

        public void Subscribe(ClassWithDelegate theClassWithDelegate)
        {
            theClassWithDelegate.theDelegate += new ClassWithDelegate.DelegateThatReturns(Doubler);
        }

        public int Doubler()
        {
            return myCounter += 2;
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            ClassWithDelegate theClassWithDelegate = new ClassWithDelegate();

            FirstSubscribe fs = new FirstSubscribe();
            fs.Subscribe(theClassWithDelegate);

            SecondSubscribe ss = new SecondSubscribe();
            ss.Subscribe(theClassWithDelegate);

            theClassWithDelegate.Run();

            Console.ReadLine();
        }
    }
}