idle state detection silverlight 4 application
Application.Current.RootVisual.MouseMove += new MouseEventHandler(RootVisual_MouseMove);
Application.Current.RootVisual.KeyDown += new KeyEventHandler(RootVisual_KeyDown);

private void RootVisual_KeyDown(object sender, KeyEventArgs e)
{
    idle = false;
}

private void RootVisual_MouseMove(object sender, MouseEventArgs e)
{
    idle = false;
}