C#计时器

class StartTimer
    {
        public uint second;
        public uint minute;
        public uint hour;
        public Label labelTimer = new Label();
        public Timer countTimer = new Timer();//定义一个计时器
        //计时函数
        public StartTimer()
        {
            labelTimer.Size = new Size(120, 20);
            this.labelTimer.Text = "00:00:00";
            this.labelTimer.TextAlign = System.Drawing.ContentAlignment.TopCenter;

            countTimer.Interval = 1000;//计时定时器初始化
            countTimer.Tick += new EventHandler(countTimer_Tick);
        }
        private string strTimer()
        {
            string timer = null;
            string timerSecond = null;
            string timerMinute = null;
            string timerHour = null;
            if (second < 59)
            {
                second++;
            }
            else
            {
                second = 0;
                if (minute < 59)
                {
                    minute++;
                }
                else
                {
                    minute = 0;
                    if (hour < 23)
                    {
                        hour++;
                    }
                    else
                    {
                        hour = 0;
                    }
                }
            }
            if (second < 10)
            {
                timerSecond = "0" + second.ToString();
            }
            else
            {
                timerSecond = second.ToString();
            }
            if (minute < 10)
            {
                timerMinute = "0" + minute.ToString();
            }
            else
            {
                timerMinute = minute.ToString();
            }
            if (hour < 10)
            {
                timerHour = "0" + hour.ToString();
            }
            else
            {
                timerHour = hour.ToString();
            }
            timer = timerHour + ":" + timerMinute + ":" + timerSecond;
            return timer;
        }
        //重置计时
        public void resetTimer()
        {
            second = 0;
            minute = 0;
            hour = 0;
            labelTimer.Text = "00:00:00";
        }
        //采集计时
        private void countTimer_Tick(object sender, EventArgs e)
        {
            labelTimer.Text = strTimer();
        }
    }