在silverlight中怎么实现计时器?在c#文件中怎么写代码?

C# code
private DispatcherTimer timer = new DispatcherTimer();

timer.Interval = new TimeSpan(0, 0, 0, 0, 1000);
timer.Tick += new EventHandler(timer_Tick);
timer.Start();

void timer_Tick(object sender, EventArgs e)
{
    //
}