PartEditBox: Binding to DropDownButtonVisibility does not work on PropertyChanged.

Hello!

My application displays objects inside a PropertyGrid. These objects can either have one or multiple values which may vary during runtime (and their display-time). When an object has multiple values, I want to display them in a pop-up. Single values shall be directly displayed in a TextBlock which is part of the PartEditBox. For this to work, I want to dynamically display the DropDownButton.

This is a part of my editor's XAML code:

<editors:PartEditBox 
 Name="EditBox" 
 BorderThickness="0"
 DropDownButtonVisibility="{Binding Path=MyObject.IsMultiValue, ElementName=EditorRoot, Mode=OneWay, 
                            UpdateSourceTrigger=PropertyChanged, Converter={StaticResource ResourceKey=Bool2Visibility}}"
 DropDownStaysOpen="False"
 DropDownContentTemplate="{StaticResource ResourceKey=DropDownContent}"
 MinDropDownWidth="250"
 MinDropDownHeight="150" 
 MaxDropDownHeight="250"
 MaxDropDownWidth="250">
  <TextBlock 
   editors:PartEditBox.ItemPlacementSlot="Center"
   Text="{Binding Path=MyObject.Value, ElementName=EditorRoot, Mode=TwoWay}"
   HorizontalAlignment="Left" 
   VerticalAlignment="Center" />
</editors:PartEditBox>

The above code works fine when the IsMultiValue-property does not change while the object is displayed on the PropertyGrid. But when IsMultiValue changes while the object is displayed in the PropertyGrid, I cannot see a difference regarding the DropDownButton.

I assume that the binding is not broken because:
 - the content of the TextBlock changes when the object's values change
 - when I de-select the to-be-displayed object and re-select it (so the PropertyGrid initializes again), the DropDownButton gets displayed.
 - the console does not display any errors

Thank you for your help,

     Till