wpf contextmenu子菜单放置

Question

What determines the placement of submenus in a contextmenu?

I create a ContextMenu dynamically and set the PlacementRectangle so that it appears in the center of the screen - so far so good.

Some of the items show a submenu. However the submenu always defaults to showing on the left. It should default to showing on the right of the parent item selected.

How do I change this?

Answer 1

This is the default for MenuItem.TopLevelItemTemplateKey

<Popup x:Name="PART_Popup" AllowsTransparency="True" Focusable="False" IsOpen="{Binding IsSubmenuOpen, RelativeSource={RelativeSource TemplatedParent}}" PopupAnimation="{DynamicResource {x:Static SystemParameters.MenuPopupAnimationKey}}" Placement="Bottom" >

Now this it default for MenuItem.SubmenuHeaderTemplateKey

 <Popup x:Name="PART_Popup" AllowsTransparency="True" Focusable="False" HorizontalOffset="-2" IsOpen="{Binding IsSubmenuOpen, RelativeSource={RelativeSource TemplatedParent}}" PopupAnimation="{DynamicResource {x:Static SystemParameters.MenuPopupAnimationKey}}" Placement="Right" VerticalOffset="-3">

Edit 1: Look for some custom style for popup defined in your App.xaml file that may be setting by default the location of all the popup in the center of the screen

Edit 2: If you are using windows with touch screen the menu appears in a position opposite to the orientation defined for right handed or left handed, this is so that the menu is not obscured by your hand when using it click here to see how to fix it