关于C#的异步委托BeginInvoke,EndInvoke,CallBack回调函数，返回值

关于C#的异步委托BeginInvoke,EndInvoke,CallBack回调函数，返回值
源码参考：

  public delegate int MyDelegate(int n1, int n2);
	    class Program
	    {
	        public static Func<int, int, int> fund;
	        static void Main(string[] args)
	        {
	            Console.WriteLine("主线程开始...");
	            //fund += SumCount;
	            MyDelegate _mydelegate = new MyDelegate(SumCount);
	            //_mydelegate.Invoke(1,10);//同步执行委托
	            #region EndInvoke异步执行
	            //IAsyncResult result = _mydelegate.BeginInvoke(1, 10, null, null);//异步执行委托
	            这两句之间可以做主线程的后续任务
	            //Console.WriteLine("主线程任务继续执行...");
	            //var reint = _mydelegate.EndInvoke(result);
	            //Console.WriteLine("线程外返回值：{0}", reint);
	            #endregion

            #region callBack  异步回调执行
            _mydelegate.BeginInvoke(1, 10, new AsyncCallback(callbackFun), "TestStr");
            #endregion

            Console.WriteLine("主线程继续...");
            Console.ReadKey();
        }

        public static void callbackFun(IAsyncResult syncresult)
        {
            //在回调函数中通过EndInvoke获得返回值
            Console.WriteLine("回调函数的参数：" + syncresult.AsyncState);
            //把接口类型转换为具体对象
            AsyncResult result = syncresult as AsyncResult;
            MyDelegate mydelegatetype = result.AsyncDelegate as MyDelegate;
            Console.WriteLine("返回值：" + mydelegatetype.EndInvoke(syncresult));
        }

        public static int SumCount(int a, int b)
        {
            Console.WriteLine("子线程开始...");
            int sum = 0;
            for (int i = a; i < b; i++)
            {
                sum += i;
                Thread.Sleep(100);
            }
            Console.WriteLine("子线程完成...");
            return sum;
        }

    }