private static void OnCommandChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
RibbonGallery gallery = (RibbonGallery)d;
ICommand oldCommand = (ICommand)e.OldValue;
ICommand newCommand = (ICommand)e.NewValue;
if (oldCommand != null)
{
gallery.UnhookCommand(oldCommand);
}
if (newCommand != null)
{
gallery.HookCommand(newCommand);
}
RibbonHelper.OnCommandChanged(d, e);
}