ComboBox issue

[fpuglap]

I have the following ComboBox in XAML:

<ComboBox Grid.Row="1" Grid.Column="1" x:Name="Data" Width="175" Foreground="White" Cursor="Hand" SelectedItem="{Binding Path=SelectedData, Mode=TwoWay}" DisplayMemberPath="Tag" materialDesign:HintAssist.Hint="Seleccionar Celda" Margin="0 0 0 0">

How to remove the background line that it's showing inside the red loop?

[Keboo]

Appears to be the same issue as #916. Functionally the issue is that we try to draw a popup control with a "hole" in it to show the underlying control. However this is a bit problematic in some cases as that popup must be positioned exactly over the combo box control