rotatetransform - wpf rotation

WPF Rotate rectangle animation in XAML (1)

How can I rotate a rectangle infinitely - ONLY within xaml definition. So far I found a solution with code but no xaml: which I use like this:

    private void Window_Loaded_1(object sender, RoutedEventArgs e)
        var da = new DoubleAnimation(360, 0, new Duration(TimeSpan.FromSeconds(1)));
        var rt = new RotateTransform();
        rect1.RenderTransform = rt;
        rect1.RenderTransformOrigin = new Point(0.5, 0.5);
        da.RepeatBehavior = RepeatBehavior.Forever;
        rt.BeginAnimation(RotateTransform.AngleProperty, da);

But how can I achieve this with XAML only?

Something like this

<Rectangle x:Name="rect1" RenderTransformOrigin="0.5, 0.5">
    <!-- giving the transform a name tells the framework not to freeze it -->
    <RotateTransform x:Name="noFreeze" />
    <EventTrigger RoutedEvent="Loaded">
            To="-360" Duration="0:0:1" RepeatBehavior="Forever" />

Of course you can remove Loaded trigger and run this storyboard whenever you want.