Error when using WPF RibbonGallery-Collection of common programming errors

The RibbonMenuItemsPanel-class of the System.Windows.Controls.Ribbon.Primitives allows to place a RibbonGallery in a RibbonGroup. This class implements the ISupportStarLayout-interface.

Define the primitives-Namespace in the Window-element (could also be RibbonWindow):

The RibbonGroup-part:

    
        
            
                ...
            
        
    

Note that i use the System.Windows.Controls.Ribbon-namespace (.Net 4.5) and not the Microsoft.Windows.Controls.Ribbon-namespace. But this should be nearly the same.