ControlTemplate for second level of TreeView - wpf

Question

I'm trying to create a TreeView which has two levels but I'm getting nowhere. I have an ItemTemplateSelector (which works - selecting either of the first two templates listed below), but I can't get the children to populate using a DataTemplate. This is my code:
public class PlannedMealGroup : INotifyPropertyChanged {
public ObservableCollection<PlannedMeal> Meals;
public Constants.MealTimes MealTime;
...// these implement INotifyPropertyChanged
}
<HierarchicalDataTemplate x:Key="groupTemplate" ItemsSource="{Binding Meals}">
<TextBlock Text="{Binding Path=MealTime}"/>
<HierarchicalDataTemplate.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<EventSetter Event="TreeViewItem.PreviewMouseRightButtonDown" Handler="tre_PreviewMouseRightButtonDown"/>
</Style>
</HierarchicalDataTemplate.ItemContainerStyle>
</HierarchicalDataTemplate>
<DataTemplate x:Key="mealTemplate">
<Border Name="Border" Margin="4,2" Padding="3" Background="Transparent" IsHitTestVisible="True" SnapsToDevicePixels="true" BorderThickness="0.6" CornerRadius="3">
<Border Name="InnerBorder" Background="Transparent" IsHitTestVisible="True">
<StackPanel Orientation="Horizontal">
<Image Source="{Binding Recipe.Icon,Converter={StaticResource IconConverter}, ConverterParameter=16}" Stretch="None" />
<TextBlock Text="{Binding Converter={StaticResource RecipeServingConverter}}"/>
</StackPanel>
</Border>
</Border>
<TreeView ItemTemplateSelector="{StaticResource PlannedMealTemplateSelector}" Style="{StaticResource GroupedTreeView}">
<TreeView.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel IsItemsHost="True" Orientation="{Binding Orientation,RelativeSource={x:Static RelativeSource.TemplatedParent}}" />
</ItemsPanelTemplate>
</TreeView.ItemsPanel>
<TreeView.ContextMenu>
...
<Style x:Key="GroupedTreeViewItem" TargetType="{x:Type TreeViewItem}">
<Setter Property="IsExpanded" Value="True"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TreeViewItem}">
<Border Name="Border" Margin="4,2" Padding="3" Background="{StaticResource GroupBackgroundBrush}" IsHitTestVisible="True" SnapsToDevicePixels="true" BorderThickness="0.6" CornerRadius="3">
<Expander Name="Exp" IsExpanded="{Binding IsExpanded, RelativeSource={RelativeSource AncestorType={x:Type TreeViewItem}},Mode=TwoWay}">
<Expander.Header>
<ContentPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
x:Name="PART_Header" ContentSource="Header"/>
</Expander.Header>
<ItemsPresenter x:Name="ItemsHost"/>
</Expander>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="GroupedTreeView" TargetType="TreeView">
<Setter Property="ItemContainerStyle" Value="{StaticResource GroupedTreeViewItem}"/>
</Style>
Thanks for any pointers.

Answer 1

This problem illuded me for hours, so I'll post this for anyone else. I needed to set the Style for the second level items in the first template's resources.
<HierarchicalDataTemplate x:Key="groupTemplate" ItemsSource="{Binding Meals}">
<TextBlock Text="{Binding Path=MealTime}"/>
<HierarchicalDataTemplate.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<EventSetter Event="TreeViewItem.PreviewMouseRightButtonDown" Handler="tre_PreviewMouseRightButtonDown"/>
<Setter Property="Background" Value="Red"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TreeViewItem}">
<ContentPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
x:Name="PART_Header" ContentSource="Header"/>
...