Convert Seconds to HH:MM:SS Format:

protected void Page_Load(object sender, EventArgs e)

    {

int seconds = 10000;

       string Time = ConvertToHHMMSS1(seconds);

       //string Time = ConvertToHHMMSS2(seconds);

lblImpCurTimePerday.Text = Time;

    }

private string ConvertToHHMMSS1(int seconds)

    {

        TimeSpan ts = new TimeSpan(0, 0, 0, seconds, 0);

        int Hours = (int)ts.TotalHours;

        return string.Format("{0}:{1}:{2}", Hours, ts.Minutes, ts.Seconds);

    }

private string ConvertToHHMMSS2(int seconds)

  {

    return string.Format("{0:00}:{1:00}:{2:00}", seconds / 3600, (seconds / 60) % 60, seconds % 60);

  }