Command doesn't work on top level MenuItem in MVVM - wpf

Question

It works fine if the MenuItem doesn't have a sub MenuItem, like this:
<MenuItem Header="Open" Command="{Binding OpenCommand}"/>
but, when I add a sub MenuItem to it, the Command doesn't work:
<MenuItem Header="Open" Command="{Binding OpenCommand}">
<MenuItem />
</MenuItem>
click event also doesn't work like this:
<MenuItem Header="Open" Click="MenuItem_Click">
<MenuItem />
</MenuItem>
when I try to add the Command to the header:
<MenuItem>
<MenuItem.Header>
<TextBlock>
<TextBlock.InputBindings>
<MouseBinding Gesture="LeftClick" Command="{Binding OpenCommand}"/>
</TextBlock.InputBindings>
Open
</TextBlock>
</MenuItem.Header>
<MenuItem />
</MenuItem>
the Command works but the sub MenuItem doesn't show.
Any help will be appreciate, and forgive my half-baked English.

Answer 1

If you have sub MenuItems the click event is used (and expected by the user) to show the sub-menu. To react upon a submenu opening use the event SubmenuOpened.
If you really want to be able to open a sub menu and click on the "Open", you could use this snipper, but I'd really not advice it:
<MenuItem SubmenuOpened="MenuItem_OnSubmenuOpened"> <!-- handle sub menu opening if desired -->
<MenuItem.Header>
<Button Click="Button_Click">Open V2</Button> <!-- handle click on "Open" if desired; doesn't open sub menu! -->
</MenuItem.Header>
<MenuItem />
</MenuItem>
Note that I have tested this with "Open" not being the top level menu item.