How to get and set properties on a flyout programmatically

[amtopel]

I'm trying to set (and sometimes get) properties on a Flyout, but my SetValue or GetValue method calls seem to be causing access violations and crashing. Here is reproducible example. If you just create a blank WinUI C++/WinRT project and put this in the myButton_Click handler:

    void MainWindow::myButton_Click(IInspectable const&, RoutedEventArgs const&)
    {
        Flyout flyout;

        TextBlock textBlock;
        textBlock.Text(L"Hello world");

        flyout.Content(textBlock);
        
        Style style;
        style.TargetType(xaml_typename<FlyoutPresenter>());

        Thickness thickness = { 500, 500, 500, 500 };
        style.SetValue(Control::PaddingProperty(), box_value(thickness));

        flyout.FlyoutPresenterStyle(style);

        flyout.ShowAt(myButton());
    }

Can anyone say what I'm doing wrong? Thanks for any help.