此項目基於.net framework 4.0

思路： 拖一個定時器控件，每秒執行一次，調用函數查詢當前運行時間並更新到label控件。

private void Form1_Load(object sender, EventArgs e)
{
    int runningSecond = Environment.TickCount / 1000;

    int days = runningSecond / 86400;

    int hours = runningSecond / 3600;
    int minutes = (runningSecond - hours * 3600) / 60;
    int second = (runningSecond - hours * 3600 - minutes * 60);

    this.label1.Text = String.Format("系統已經運行了{0}天{1}小時{2}分鐘{3}秒", days, hours, minutes, second);

}

///
/// 定時器： 每秒執行一次
///
///
///
private void timer1_Tick(object sender, EventArgs e)
{

    int runningSecond = Environment.TickCount / 1000;

    int days = runningSecond / 86400;

    int hours = runningSecond / 3600;
    int minutes = (runningSecond - hours * 3600) / 60;
    int second = (runningSecond - hours * 3600 - minutes * 60);

    this.label1.Text = String.Format("系統已經運行了{0}天{1}小時{2}分鐘{3}秒", days, hours, minutes, second);
}

系統運行時間懸浮框（demo）