Hi!,
Today I just want to provide a quick fix for removing Black Background Popup in WPF.
For removing Black Background you just need to set AllowsTransparency property to True, and that’s all 😉
And, off course, after that you can insert a Border, as well as a Grid, and setting your preferred background color.

<Popup PlacementTarget="{Binding ElementName=myUIElement}"
           Placement="Center" 
           AllowsTransparency="True"
           HorizontalAlignment="Center" 
           VerticalAlignment="Center" >

   <Border Background="White" ...
      ...
   </Border>

</Popup>

Marzio.