How to stretch TreeViewItem width to fill parent?

Question

I have a WPF TreeView and I want to stretch the TreeViewItem to the entire space like its parent.

<TreeView Name="treeFamilies" AllowDrop="True" >
    <TreeView.Resources>
        <HierarchicalDataTemplate DataType="{x:Type local:MyNode}" ItemsSource="{Binding Members}">
            <StackPanel Orientation="Horizontal">
                <TextBlock Text="{Binding Name}" Background="LightGray"/>
                <TextBlock Text=" [" Foreground="Blue" Background="LightGray"/>
                <TextBlock Text="{Binding Members.Count}" Foreground="Blue" Background="LightGray"/>
                <TextBlock Text="]" Foreground="Blue" Background="LightGray" />
            </StackPanel>
        </HierarchicalDataTemplate>
    </TreeView.Resources>
    <TreeView.ItemContainerStyle>
        <Style TargetType="{x:Type TreeViewItem}">
            <Setter Property="HorizontalContentAlignment" Value="Stretch"/>
        </Style>
    </TreeView.ItemContainerStyle>
</TreeView>

It seems I'm using the ItemContainer style <Setter Property="HorizontalContentAlignment" Value="Stretch"/> wrongly. My current tree is looking like this picture:

I want tho strech the gray background to fill the entire end of the treeview control. How could I achieve this?

Answer 1

Form Il Vic's comment, this msdn blog shows a hack-like way to remove the last column from TreeViewItem.

In case the blog shut down, I copy my working code here. After a TreeViewItem is loaded, I remove the 3rd ColumnDefinition from the grid, and set 2nd ColumnDefinition width to *;

public class StretchingTreeViewItem : TreeViewItem
{
    public StretchingTreeViewItem()
    {
        this.Loaded += new RoutedEventHandler(StretchingTreeViewItem_Loaded);
    }

    private void StretchingTreeViewItem_Loaded(object sender, RoutedEventArgs e)
    {
        if (this.VisualChildrenCount > 0)
        {
            Grid grid = this.GetVisualChild(0) as Grid;
            if (grid != null && grid.ColumnDefinitions.Count == 3)
            {
                grid.ColumnDefinitions.RemoveAt(2);
                grid.ColumnDefinitions[1].Width = new GridLength(1, GridUnitType.Star);
            }
        }
    }

    protected override DependencyObject GetContainerForItemOverride()
    {
        return new StretchingTreeViewItem();
    }

    protected override bool IsItemItsOwnContainerOverride(object item)
    {
        return item is StretchingTreeViewItem;
    }
}

Then I override TreeView to get the custom items.

public class StretchingTreeView : TreeView
{
    protected override DependencyObject GetContainerForItemOverride()
    {
        return new StretchingTreeViewItem();
    }

    protected override bool IsItemItsOwnContainerOverride(object item)
    {
        return item is StretchingTreeViewItem;
    }        
}