WPF Trigger for IsSelected in a DataTemplate for ListBox items

Question

I have a ListBox set up with a series of DataTemplates to properly display the contents, based on the type of data. What I am trying trigger the look of each DataTemplate to change from a "read-only" to an "editable" state when the ListBoxItem is selected. My goal was to set this up with an "IsSelected" trigger, and show/hide controls accordingly.

I define my DataTemplates in the following way:

    <DataTemplate DataType="{x:Type vm:HeaderSlugViewModel}">
        <vw:HeaderSlugView />
    </DataTemplate>

    <DataTemplate DataType="{x:Type vm:ContentSlugViewModel}">
        <vw:ContentSlugView />
    </DataTemplate>

    <DataTemplate DataType="{x:Type vm:ImageSlugViewModel}">
        <vw:ImageSlugView />
    </DataTemplate>

Each "View" is an independent XAML file. I'd like to be able to set up the triggers in those files, looking at the ListBoxItem's IsSelected property, in order to control the visibility of the various controls within.

The template to override the ListBoxItem follows:

    <Style TargetType="{x:Type ListBoxItem}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type ListBoxItem}">
                    <Border Name="SlugContainer" Background="Transparent" BorderBrush="Black" BorderThickness="1" CornerRadius="2" Margin="0,5,0,0" Padding="5">
                        <Grid>
                            <Grid.RowDefinitions>
                                <RowDefinition Height="Auto" />
                                <RowDefinition Height="*" />
                            </Grid.RowDefinitions>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="*" />
                            </Grid.ColumnDefinitions>

                            <!-- snipped for brevity -->

                            <ContentPresenter Grid.Row="1" />

                        </Grid>
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

I modified the ContentPresenter in the following way in order to test out using the "FindAncestor" RelativeSource:

<ContentPresenter Grid.Row="1">
    <ContentPresenter.Style>
        <Style TargetType="{x:Type ContentPresenter}">
            <Setter Property="Visibility" Value="Collapsed" />
            <Style.Triggers>
                <DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor,AncestorType={x:Type ListBoxItem}}, Path=IsSelected}" Value="True">
                    <Setter Property="Visibility" Value="Visible"/>
                </DataTrigger>
                <DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor,AncestorType={x:Type ListBoxItem}}, Path=IsSelected}" Value="False">
                    <Setter Property="Visibility" Value="Collapsed"/>
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </ContentPresenter.Style>
</ContentPresenter>

This works, but when I move similar code into the XAML file representing a View it no longer sees the trigger. For example:

<UserControl ...>
    <UserControl.Resources>
        <local:FlowDocumentToXamlConverter x:Key="flowDocumentConverter" />
    </UserControl.Resources>

    <UserControl.Style>
        <Style TargetType="{x:Type UserControl}">
            <Style.Triggers>
                <DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ListBoxItem}}, Path=IsSelected}">
                    <Setter Property="Visibility" Value="Hidden" />
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </UserControl.Style>

    <DockPanel Name="SlugContainer">
        <Label DockPanel.Dock="Top" Content="Filler" />
        <ctrl:BindableRichTextBox x:Name="TextBox" Document="{Binding Content, Converter={StaticResource flowDocumentConverter}, Mode=TwoWay}" LostFocus="OnLostFocus" />
    </DockPanel>
</UserControl>

How can I detect, preferably from the View's XAML file, when the ListBoxItem has been selected?

Thank you for any help!

Rune Andersen Rune Andersen · Accepted Answer · 2011-06-13T21:00:46

2

votes

You are missing:

Value="True"

in your View - could it be that?

WPF Trigger for IsSelected in a DataTemplate for ListBox items

1 Answers