Treeview with wrappanel - flexible grouping - wpf

Question

I'n trying to resolve problem with treeview.
I would like to get items (UserControls) ordered inside wrappanel, in treeview node.
-Group
|---------------------------------------------|
|Item Item Item Item Item Item Item Item Item |
|---------------------------------------------|
+Group
+Group
If window width (and along treeview width) suppress and items wont fit to one line, those should be ordered to next line.
-Group
|-------------------------|
|Item Item Item Item Item |
|Item Item Item Item |
|-------------------------|
+Group
+Group
I have done above example which won't put items on next row. This is working without Treeview, but inside treeview-node something is missing..
<DataTemplate x:Key="GroupTemplateFrontPage">
<Border BorderBrush="AliceBlue" BorderThickness="1" CornerRadius="10"
Background="{StaticResource TreeViewItemBackground}" >
<Expander HeaderTemplate="{DynamicResource HeaderTemplate}"
Header="{Binding}" IsTabStop="False" HorizontalAlignment="Left"
IsEnabled="True" ExpandDirection="Down" IsExpanded="True">
<Grid Margin="5,5,5,5">
<Grid.ColumnDefinitions>
<ColumnDefinition />
</Grid.ColumnDefinitions>
<ListBox Margin="10,39,0,0" VerticalAlignment="Top" ScrollViewer.VerticalScrollBarVisibility="Disabled" ScrollViewer.HorizontalScrollBarVisibility="Disabled" ItemsSource="{Binding Modems}">
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel
HorizontalAlignment="Stretch"
ScrollViewer.HorizontalScrollBarVisibility="Disabled"
ScrollViewer.VerticalScrollBarVisibility="Disabled"/>
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
<ListBox.ItemTemplate>
<DataTemplate>
<Grid>
<Controls:UserControlItem Margin="4" />
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
</Expander>
</Border>
</DataTemplate>
<StackPanel Orientation="Vertical">
<TextBlock Text="Treeview" />
<TreeView Name="_treeView" ScrollViewer.HorizontalScrollBarVisibility="Disabled"
Margin="0,0,0,0"
ItemsSource="{Binding}"
ItemTemplate="{StaticResource GroupTemplateFrontPage}" />
</StackPanel>

Answer 1

Setting the ItemsPanel for TreeViewItems should do:
<TreeView.ItemContainerStyle>
<Style TargetType="TreeViewItem">
<Setter Property="ItemsPanel">
<Setter.Value>
<ItemsPanelTemplate>
<WrapPanel />
</ItemsPanelTemplate>
</Setter.Value>
</Setter>
</Style>
</TreeView.ItemContainerStyle>
Also turn off horizontal scrolling to allow for wrapping:
<TreeView ScrollViewer.HorizontalScrollBarVisibility="Disabled" ...>