protected override void OnKeyDown(KeyEventArgs e)
{
RibbonHelper.HandleDropDownKeyDown(this, e,
delegate { return IsDropDownOpen; },
delegate(bool value) { IsDropDownOpen = value; },
RetainFocusOnEscape ? _partToggleButton : null,
_popup.TryGetChild());
// Do not call base because base's logic interferes
// with that of RibbonMenuButton.
// base.OnKeyDown(e);
if (e.Handled)
return;
OnNavigationKeyDown(e);
}