public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        
        {  for (; ; )
           {
            
               textBox1.Text = DateTime.Now.ToLongTimeString();
              System.Threading.Thread.Sleep(1000);
           }
        }  窗体中一个textbox（显示系统时间）和一个button

关键是还没有学到times控件那里