ListBox of expanders not acting like radiobuttons - wpf

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... :]