Wpf Animation Change RepeatBehavior

I have animated fan working forever, but I want to stop it with a second event like button click etc. Is it possible to change value of RepeatBehavior or am I have to use Storyboard or anything else ?

Here my code;

private void button_Click(object sender, RoutedEventArgs e)
    {
        DoubleAnimation da = new DoubleAnimation(0, 360, TimeSpan.FromSeconds(0.1));
        RotateTransform rt = new RotateTransform();
        Fan.RenderTransform = rt;
        da.RepeatBehavior = RepeatBehavior.Forever;
        Fan.RenderTransformOrigin = new Point(0.5, 0.5);
        rt.BeginAnimation(RotateTransform.AngleProperty, da);    

    }