DropDownButton popup placement

[GAMP]

You explicitly set placement in code thus its not possible to do it in style

 private static void IsExpandedPropertyChangedCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
        {
            DropDownButton button = (DropDownButton)dependencyObject;
            if (button.clickButton != null)
            {
               button.menu.Placement = PlacementMode.Bottom;
                button.menu.PlacementTarget = button.clickButton;
            }
        }