ListBox of expanders not acting like radiobuttons

Question

I have created a listbox of expanders like this question: Expander Auto Open/Close

The solution works with content in the expanders when the listbox is the only item on the window.

But when I try to use the same code with my custom control, I'm getting this error:

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='System.Windows.Controls.ListBoxItem', AncestorLevel='1''. BindingExpression:Path=IsSelected; DataItem=null; target element is 'Expander' (Name=''); target property is 'IsExpanded' (type 'Boolean')

I've tried adding the IsSelected Property in the ListBox.ItemContainerStyle as one poster suggested in another thread but that failed.

<ListBox Margin="5"
         SelectionMode="Single"
         ScrollViewer.VerticalScrollBarVisibility="Auto">
    <ListBox.Resources>
        <Style TargetType="{x:Type Expander}">
             <Setter Property="IsExpanded"
                     Value="{Binding Path=IsSelected, RelativeSource={RelativeSource AncestorType={x:Type ListBoxItem}}}" />
        </Style>
        <Style TargetType="{x:Type controls:SelectionCriteriaControl}">
             <Setter Property="MaxHeight"
                     Value="200" />
        </Style>
    </ListBox.Resources>
    <Expander Header="Fund Family" Margin="2">
        <StackPanel>
            <controls:SelectionCriteriaControl DataContext="{Binding FundFamilySelectionCriteria, Mode=TwoWay}" />
        </StackPanel>
    </Expander>
    <Expander Header="Asset Class" Margin="2">
        <StackPanel>
            <controls:SelectionCriteriaControl DataContext="{Binding AssetClassSelectionCriteria, Mode=TwoWay}" />
        </StackPanel>
    </Expander>
    <ListBox.Template>
        <ControlTemplate TargetType="{x:Type ListBox}">
            <ItemsPresenter />
        </ControlTemplate>
    </ListBox.Template>
    <ListBox.ItemContainerStyle>
        <Style TargetType="{x:Type ListBoxItem}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type ListBoxItem}">
                        <ContentPresenter Content="{TemplateBinding Content}" />
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </ListBox.ItemContainerStyle>
</ListBox>

Fails miserably!!!!!

Any help appreciated :)

Answer 1

It's a bit of a large scenario for me to set up at the moment, but something that comes to mind to try:

Value="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=IsSelected}" />

I don't think where templates are used that you can define relative sources by type.

Edit: This code worked fine: Based on your original, the TemplatedParent wasn't necessary.

    <Grid>
    <Grid.RowDefinitions>
        <RowDefinition/>
        <RowDefinition Height="auto"/>
    </Grid.RowDefinitions>
    <ListBox x:Name="testList" Margin="5"
     SelectionMode="Single"
     ScrollViewer.VerticalScrollBarVisibility="Auto">
        <ListBox.Resources>
            <Style TargetType="{x:Type Expander}">
                <Setter Property="IsExpanded"
                 Value="{Binding Path=IsSelected, RelativeSource={RelativeSource AncestorType={x:Type ListBoxItem}}}" />
            </Style>
        </ListBox.Resources>
        <Expander Header="Fund Family" Margin="2">
            <StackPanel>
                <TextBlock Text="First"/>
                <TextBlock Text="Second"/>
            </StackPanel>
        </Expander>
        <Expander Header="Asset Class" Margin="2">
            <StackPanel>
                <TextBlock Text="First"/>
                <TextBlock Text="Second"/>
            </StackPanel>
        </Expander>
        <ListBox.Template>
            <ControlTemplate TargetType="{x:Type ListBox}">
                <ItemsPresenter />
            </ControlTemplate>
        </ListBox.Template>
        <ListBox.ItemContainerStyle>
            <Style TargetType="{x:Type ListBoxItem}">
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="{x:Type ListBoxItem}">
                            <ContentPresenter Content="{TemplateBinding Content}" />
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>
        </ListBox.ItemContainerStyle>
    </ListBox>
    <Button HorizontalAlignment="Left" Content="Test" Grid.Row="1" Width="60" Click="Button_Click"/>
</Grid>

And a quick code-behind to trigger a programmatic SelectedIndex set...

        private void Button_Click(object sender, RoutedEventArgs e)
    {
        testList.SelectedIndex = 1;
    }

Seems to work fine for me. Clicking on a list item expands, and even using the button to set it specifically by setting the selected index it expands. Something very fishy is affecting your specific scenario... :]