Accessing the border around a contentpresenter

Question

I have a ListView which uses a DataTemplate. When an item is selected a border and background is added but I am unsure where from. This shows in the visual tree as a border around the ContentPresenter but inside the ListViewItem. The properties show that they were added by triggers in the TemplatedParent template. How can I override these triggers given the structure below or is my approach wrong?

<ListView x:Name="MyListview" ItemsSource="{Binding Thumbnails}"    ScrollViewer.HorizontalScrollBarVisibility="Disabled">
    <ListView.ItemsPanel>
        <ItemsPanelTemplate>
            <local:VirtualizingWrapPanel IsItemsHost="True" ....../>
        </ItemsPanelTemplate>
    </ListView.ItemsPanel>
    <ListView.ItemContainerStyle>
        <Style TargetType="ListViewItem">
            <Setter Property="SnapsToDevicePixels" Value="true" />
        </Style>
    </ListView.ItemContainerStyle>
    <ListView.ItemTemplate>
        <DataTemplate x:Name="ThumbItemTemplate" DataType="{x:Type local:ThumbItem}"> 
            <Grid Margin="6" Width="128"  Height="168">
                <Grid.RowDefinitions>
                    <RowDefinition Height="128"></RowDefinition>
                    <RowDefinition></RowDefinition>
                </Grid.RowDefinitions>
                <Border Grid.Row="0" BorderThickness="0">
                    <Image x:Name="ThumbnailImage" MaxHeight="128" MaxWidth="128" Source="{Binding Thumbnail}" />
                </Border>
                <TextBlock Grid.Row="1" Margin="0,6,0,0" TextAlignment="Center" x:Name="Description" Text="{Binding Title}" />
            </Grid>        
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

Answer 1

These come from the ItemContainerStyle. You could define your own custom template for the ListViewItem, e.g:

<Style TargetType="ListViewItem">
    <Style.Resources>
        <Style x:Key="FocusVisual">
            <Setter Property="Control.Template">
                <Setter.Value>
                    <ControlTemplate>
                        <Rectangle Margin="2" SnapsToDevicePixels="true" Stroke="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}" StrokeThickness="1" StrokeDashArray="1 2"/>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
        <SolidColorBrush x:Key="Item.MouseOver.Background" Color="#1F26A0DA"/>
        <SolidColorBrush x:Key="Item.MouseOver.Border" Color="#a826A0Da"/>
        <SolidColorBrush x:Key="Item.SelectedInactive.Background" Color="#3DDADADA"/>
        <SolidColorBrush x:Key="Item.SelectedInactive.Border" Color="#FFDADADA"/>
        <SolidColorBrush x:Key="Item.SelectedActive.Background" Color="#3D26A0DA"/>
        <SolidColorBrush x:Key="Item.SelectedActive.Border" Color="#FF26A0DA"/>
    </Style.Resources>
    <Setter Property="SnapsToDevicePixels" Value="True"/>
    <Setter Property="Padding" Value="4,1"/>
    <Setter Property="HorizontalContentAlignment" Value="{Binding HorizontalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
    <Setter Property="VerticalContentAlignment" Value="{Binding VerticalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
    <Setter Property="Background" Value="Transparent"/>
    <Setter Property="BorderBrush" Value="Transparent"/>
    <Setter Property="BorderThickness" Value="1"/>
    <Setter Property="FocusVisualStyle" Value="{StaticResource FocusVisual}"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="ListViewItem">
                <Border x:Name="Bd" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="true">
                    <ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
                </Border>
                <ControlTemplate.Triggers>
                    <MultiTrigger>
                        <MultiTrigger.Conditions>
                            <Condition Property="IsMouseOver" Value="True"/>
                        </MultiTrigger.Conditions>
                        <Setter Property="Background" TargetName="Bd" Value="{StaticResource Item.MouseOver.Background}"/>
                        <Setter Property="BorderBrush" TargetName="Bd" Value="{StaticResource Item.MouseOver.Border}"/>
                    </MultiTrigger>
                    <MultiTrigger>
                        <MultiTrigger.Conditions>
                            <Condition Property="Selector.IsSelectionActive" Value="False"/>
                            <Condition Property="IsSelected" Value="True"/>
                        </MultiTrigger.Conditions>
                        <Setter Property="Background" TargetName="Bd" Value="{StaticResource Item.SelectedInactive.Background}"/>
                        <Setter Property="BorderBrush" TargetName="Bd" Value="{StaticResource Item.SelectedInactive.Border}"/>
                    </MultiTrigger>
                    <MultiTrigger>
                        <MultiTrigger.Conditions>
                            <Condition Property="Selector.IsSelectionActive" Value="True"/>
                            <Condition Property="IsSelected" Value="True"/>
                        </MultiTrigger.Conditions>
                        <Setter Property="Background" TargetName="Bd" Value="{StaticResource Item.SelectedActive.Background}"/>
                        <Setter Property="BorderBrush" TargetName="Bd" Value="{StaticResource Item.SelectedActive.Border}"/>
                    </MultiTrigger>
                    <Trigger Property="IsEnabled" Value="False">
                        <Setter Property="TextElement.Foreground" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
                    </Trigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

You can copy the default template by right-clicking on a ListBox in design mode in Visual Studio and choose Edit Additional Templates->Edit Generated Item Container (ItemContainerStyle).