private delegate void FlushClient(); //委托        private void Form1_Load(object sender, EventArgs e)        {            Thread thread = new Thread(ThreadFunction); //创建一个线程　　            thread.IsBackground = true;            thread.Start();        }        private void ThreadFunction()        {            while (true)            {                FlushClient fc = new FlushClient(CrossThreadFlush); //使用委托                this.BeginInvoke(fc);                Thread.Sleep(1000);            }        }        private void CrossThreadFlush()        {            label1.Text = (DateTime.Now.ToString() + "\n");            Thread.Sleep(1000);        }