I have a UserControl which defines a Time/Date spinner control. If set the UserControl's Effect and Background properties, then the control simply does not show up. So, I had to set the background on the UserControl and the Effect on the child Grid to get it to work.

The same thing happens if I try to set both on the child Grid, the entire control is not rendered (all I see is the background).

<UserControl x:Class="Controls.DateTimeControl.DateTimeSpinner"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:noesis="clr-namespace:NoesisGUIExtensions;assembly=Noesis.GUI.Extensions"
xmlns:local="clr-namespace:Controls.DateTimeControl">
<UserControl.Background>
<SolidColorBrush Color="Black" Opacity=".5"></SolidColorBrush>
</UserControl.Background>
<UserControl.Resources>
<!-- Control resources and styles here -->
</UserControl.Resources>
<Grid Effect="{StaticResource StandardDropShadow}" Focusable="True" FocusVisualStyle="{x:Null}" Background="Transparent" PreviewKeyDown="OnPreviewKeyDown" Loaded="OnLoaded" Height="200" Width="800" HorizontalAlignment="Center" VerticalAlignment="Center">
<!-- Control defined here -->
</Grid>
</UserControl>