System.Timers.Timer t = new System.Timers.Timer(5000); //设置时间间隔为5秒

        private void Form1_Load(object sender, EventArgs e)
        {
            t.Elapsed += new System.Timers.ElapsedEventHandler(Timer_TimesUp);
            t.AutoReset = false; //每到指定时间Elapsed事件是触发一次(false),还是一直触发(true)
        }
        
        private void btnStart_Click(object sender, EventArgs e)
        {
            t.Enabled = true; //是否触发Elapsed事件
            t.Start();
        }

        private void Timer_TimesUp(object sender, System.Timers.ElapsedEventArgs e)
        {
            //到达指定时间5秒触发该事件输出 Hello World!!!!
            System.Diagnostics.Debug.WriteLine("Hello World!!!!");
        }

        private void btnStop_Click(object sender, EventArgs e)
        {
            t.Stop();
            System.Diagnostics.Debug.WriteLine("未到指定时间5秒提前终结!!!");
        }