public class Global : System.Web.HttpApplication
{
    Timer timerUpdate = new Timer();

    protected void Application_Start(object sender, EventArgs e)
    {
        timerUpdate.Interval = 1000;
        timerUpdate.Elapsed += TimerUpdate_Elapsed;
        timerUpdate.Start();
    }

    private void TimerUpdate_Elapsed(object sender, ElapsedEventArgs e)
    {
        timerUpdate.Stop();

        // do something
    }
}