Timer unter C#

private DispatcherTimer _testtimer = new DispatcherTimer();

private void startTestTimer()
{
  _testtimer.Tick += new EventHandler(_testtimer_Tick);
  _testtimer.Interval = new TimeSpan(0, 0, 1);
  _testtimer.Start();
}

private void _testtimer_Tick(object sender, EventArgs e)
{
  this.Title = DateTime.Now.Hour + ":" + 
    DateTime.Now.Minute + ":" + 
    DateTime.Now.Second;
}