异步 BeginInvoke

委托的异步调用
异步多线程的三大特点：
1.同步方法卡界面，原因是主线程被占用；异步方法不卡界面，原因是计算交给了别的线程，主线程空闲
2.同步方法慢，原因是只有一个线程计算；异步方法快，原因是多个线程同事计算，但是更消耗资源，不宜太多
3.建议线程的数量不要超过 CPU核数*4
4.异步多线程是无序的，启动顺序不确定、执行时间不确定、结束时间不确定

        private void btnAsync_Click(object sender, EventArgs e)
        {
            Stopwatch watch = new Stopwatch();
            watch.Start();
            Console.WriteLine();
            Console.WriteLine("********************btnAsync_Click Start 主线程id={0}********************", Thread.CurrentThread.ManagedThreadId);
            Func <string,string> method = new Func<string,string >(this.TestThread);
            IAsyncResult[] asyncResult = new IAsyncResult[5];

            for (int i = 0; i < 5; i++)
            {
                //在这个BeginInvoke方法是拿不到委托函数的返回值的
                //第二个参数是一个委托（AsyncCallback）,输入是异步调用的返回值
                asyncResult[i] = method.BeginInvoke(string.Format("btnAsync_Click_{0}", i), t =>//异步调用的返回值
              {
                  //Console.WriteLine(t.Equals(asyncResult));//这里证明t就是异步调用的返回值
                  //Console.WriteLine(t.AsyncState);//显示状态参数：yoyo_{0}
                  Console.WriteLine("这里是回调函数 {0}", Thread.CurrentThread.ManagedThreadId);
              }, string.Format ("yoyo_{0}",i)); //最后是一个状态参数
            }

            //做一个计时器等待异步完成
            /* int j = 1;
             while(!asyncResult[0].IsCompleted || !asyncResult[1].IsCompleted || !asyncResult[2].IsCompleted || !asyncResult[3].IsCompleted || !asyncResult[4].IsCompleted)
             {
                 Console.WriteLine("**********正在计算，已完成{0}%**********",10*j++);
                 Thread.Sleep(200);
             }*/


            //WaitOne不能拿到委托函数的返回值
            /*   asyncResult[0].AsyncWaitHandle.WaitOne();         //一直等待这个异步结束
               //asyncResult[0].AsyncWaitHandle.WaitOne(-1);  //一直等待这个异步结束
               //asyncResult[0].AsyncWaitHandle.WaitOne(200);//只等200毫秒
               asyncResult[1].AsyncWaitHandle.WaitOne();
               asyncResult[2].AsyncWaitHandle.WaitOne();
               asyncResult[3].AsyncWaitHandle.WaitOne();
               asyncResult[4].AsyncWaitHandle.WaitOne();*/

            //Eninvoke可以拿到委托函数的返回值
            Console.WriteLine(method.EndInvoke(asyncResult[0]));
            Console.WriteLine(method.EndInvoke(asyncResult[1]));
            Console.WriteLine(method.EndInvoke(asyncResult[2]));
            Console.WriteLine(method.EndInvoke(asyncResult[3]));
            Console.WriteLine(method.EndInvoke(asyncResult[4]));

            watch.Stop();
            Console.WriteLine("********************btnAsync_Click End 主线程id={0}  {1}********************", Thread.CurrentThread.ManagedThreadId, watch.ElapsedMilliseconds);
            Console.WriteLine();
        }

       private string TestThread(string name)
        {
            Console.WriteLine("TestThread Start Name={2},当前线程的id:{0},当前时间为{1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString("hh:mm:ss:fff"), name);
            long Sum = 0;
            for (int i = 1; i < 999999999; i++)
            {
                Sum += i;
            }
            //Thread.Sleep(2000);
            Console.WriteLine("TestThread End Name={2},当前线程的id:{0},当前时间为{1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString("hh:mm:ss:fff"), name);
            return string.Format("运行结果为：{0}  {1}", name, Sum);
        }