为什么数据绑定ContextMenu项目不隐藏？

I wan't to hide/show menuitems in a contextmenu using some propery of databound object. But my menuitems don't hide, they behave as if their Visiblity would be set to Visibility.Hidden (not Visibility.Collapsed as it really is), what's the reason of such behaviour?I wan't to hide/show menuitems in a contextmenu