private void Form1_Load(object sender, EventArgs e)
        {
            txtDateNow.Text = DateTime.Now.ToString("yyyy-MM-dd hh:mm:ss");
            ThreadPool.QueueUserWorkItem(new WaitCallback(SetDateTimeNow));
        }

        void SetDateTimeNow(Object o)
        {
            while (true)
            {
                Thread.Sleep(1000);
                txtDateNow.Invoke(new Action(() =>
                {
                    txtDateNow.Text = DateTime.Now.ToString("yyyy-MM-dd hh:mm:ss");
                }));
            }
        }