How to implement the ThemeHelper that populates an existing RibbonGalleryBarItem or any menu with items

This example demonstrates how to implement the WinForm SkinHelper class functionality in WPF applications (ThemeHelper) that populate an existing RibbonGalleryBarItem or any menu (PopupMenu or BarSubItem) with items that correspond to DevExpress themes.

The basic logic is implemented in the ThemeHelper class.

Update:

Starting with v14.1, we introduced the Behavior class' special RibbonGalleryItemThemeSelectorBehavior and BarSubItemThemeSelectorBehavior descendants that automatically populate the corresponding BarSubItem and RibbonGalleryBarItem items with all available themes:

[XAML]
<dxr:RibbonGalleryBarItemx:Name="ribbonGalleryBarItem1"....><dxmvvm:Interaction.Behaviors><dxr:RibbonGalleryItemThemeSelectorBehavior/></dxmvvm:Interaction.Behaviors>