How can I set ScrollContentPresenter a backgroundcolor? - wpf

Question

How can I give ScrollContentPresenter a backgroundcolor? is the same question, but I set the Background on the Parent of the ScrollContentPresenter. It is the Grid and it does not work for me. I can not change the background.
<Style x:Key="ScrollViewerStyle" TargetType="{x:Type ScrollViewer}">
<Setter Property="OverridesDefaultStyle" Value="True" />
<Setter Property="VerticalAlignment" Value="Stretch"/>
<Setter Property="HorizontalAlignment" Value="Stretch"/>
<Setter Property="FontSize" Value="14"/>
<Setter Property="Foreground" Value="White"/>
<Setter Property="FocusVisualStyle" Value="{x:Null}"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ScrollViewer}">
<Border x:Name="border" BorderBrush="{Binding L1, Source={x:Static color:DesignBrushCollection.DesignColors}}" BorderThickness="1">
<Grid x:Name="Grid" Background="Transparent">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="auto"/>
</Grid.ColumnDefinitions>
<Grid Background="Red">
<ScrollContentPresenter x:Name="PART_ScrollContentPresenter" CanContentScroll="{TemplateBinding CanContentScroll}" CanHorizontallyScroll="False" CanVerticallyScroll="False" ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" Grid.Column="0" />
</Grid>
<ScrollBar x:Name="PART_VerticalScrollBar" AutomationProperties.AutomationId="VerticalScrollBar" Cursor="Arrow" Grid.Column="1" Maximum="{TemplateBinding ScrollableHeight}" Minimum="0" Visibility="{TemplateBinding ComputedVerticalScrollBarVisibility}" Value="{Binding VerticalOffset, Mode=OneWay, RelativeSource={RelativeSource TemplatedParent}}" ViewportSize="{TemplateBinding ViewportHeight}"
Style="{DynamicResource ScrollBarStyle}"/>
</Grid>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="true">
<Setter Property="BorderBrush" TargetName="border"
Value="{Binding AC3, Source={x:Static color:DesignBrushCollection.DesignColors}}"/>
</Trigger>
<Trigger Property="IsFocused" Value="true">
<Setter Property="BorderBrush" TargetName="border"
Value="{Binding AC3, Source={x:Static color:DesignBrushCollection.DesignColors}}"/>
<Setter Property="Background" TargetName="border"
Value="{Binding BG1, Source={x:Static color:DesignBrushCollection.DesignColors}}"/>
</Trigger>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="Opacity" TargetName="border" Value="0.5"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</UserControl.Resources>
<Grid Width="auto" Height="auto">
<Grid.RowDefinitions>
<RowDefinition Height="15" />
<RowDefinition Height="3" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions >
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<local:CommonLabel RequiredMark="{Binding RelativeSource={RelativeSource FindAncestor,
AncestorType={x:Type local:CommonComboBox}},Path=RequiredMark}"
FontSize="13" Padding="0"
Content="{Binding RelativeSource={RelativeSource FindAncestor,
AncestorType={x:Type local:CommonComboBox}},Path=Content}"
Grid.Row="0" Height="16" Width="139"
Margin="0,0,0,0" VerticalAlignment="Top" HorizontalAlignment="Left" Grid.ColumnSpan="2" />
<ScrollViewer Style="{StaticResource ScrollViewerStyle}" VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Disabled" Grid.Row="2">
<TextBox x:Name="TextField" TextWrapping="Wrap" BorderThickness="0" CaretBrush="{Binding AC3, Source={x:Static color:DesignBrushCollection.DesignColors}}"
Text="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:CommonTextField}},Path=Content,Mode=OneWay}" >
</TextBox>
</ScrollViewer>
</Grid>
</UserControl>

Answer 1

TextBox.Background does override the ScrollViewer.Background. If you set TextBox.Background = "Transparent" or TextBox.Background = "{x:Null}" you will see ScrollViewer.Background.
<TextBox x:Name="TextField" Background="Transparent" ... />
Be aware, that ScrollViewer.IsFocused set to true if you click the border of ScrollViewer or set the focus in code behind, not if you input a text in the TextBox.