Selecting a ListBoxItem when its inner ComboBox is focused

Question

I have a DataTemplate that will be a templated ListBoxItem, this DataTemplate has a ComboBox in it which when it has focus I want the ListBoxItem that this template represents to become selected, this looks right to me. but sadly enough it doesn't work =(

So the real question here is within a DataTemplate is it possible to get or set the value of the ListBoxItem.IsSelected property via a DataTemplate.Trigger?

<DataTemplate x:Key="myDataTemplate" 
              DataType="{x:Type local:myTemplateItem}">

 <Grid x:Name="_LayoutRoot">
     <ComboBox x:Name="testComboBox" />
 </Grid>

 <DataTemplate.Triggers>
     <Trigger Property="IsFocused" value="true" SourceName="testComboBox">
         <Setter Property="ListBoxItem.IsSelected" Value="true" />
     </Trigger>
 </DataTemplate.Triggers>

</DataTemplate>

<ListBox ItemTemplate="{StaticResource myDataTemplate}" />

Answer 1

I found a solution for your problem.

The problem is that when you have a control on your listboxitem, and the control is clicked (like for inputting text or changing the value of a combobox), the ListBoxItem does not get selected.

this should do the job:

public class FocusableListBox : ListBox
{
    protected override bool IsItemItsOwnContainerOverride(object item)
    {
        return (item is FocusableListBoxItem);
    }

    protected override System.Windows.DependencyObject GetContainerForItemOverride()
    {
        return new FocusableListBoxItem();
    }
}

--> Use this FocusableListBox in stead of the default ListBox of WPF.

And use this ListBoxItem:

public class FocusableListBoxItem : ListBoxItem
{
    public FocusableListBoxItem()
    {
        GotFocus += new RoutedEventHandler(FocusableListBoxItem_GotFocus);
    }


    void FocusableListBoxItem_GotFocus(object sender, RoutedEventArgs e)
    {
        object obj = ParentListBox.ItemContainerGenerator.ItemFromContainer(this);
        ParentListBox.SelectedItem = obj;
    }

    private ListBox ParentListBox
    {
        get
        {
            return (ItemsControl.ItemsControlFromItemContainer(this) as ListBox);
        }
    }

}

A Treeview does also have this problem, but this solution does not work for a Treeview, 'cause SelectedItem of Treeview is readonly. So if you can help me out with the Treeview please ;-)

Answer 2

No idea why your trigger don't work. To catch the get focus event of the combo box (or any control inside a listbox item) you can use attached routed events. You could put the code also in a derived listbox if you need this behavior in other parts of your application.

XAML:

<Window x:Class="RoutedEventDemo.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:Specialized="clr-namespace:System.Collections.Specialized;assembly=System"
    xmlns:System="clr-namespace:System;assembly=mscorlib"
    Height="300" Width="300">

    <Window.Resources>

        <DataTemplate x:Key="myDataTemplate">
            <Grid>
                <StackPanel Orientation="Horizontal">
                    <TextBlock Text="{Binding}" Margin="5,0"/>
                    <ComboBox Width="50">
                        <ComboBoxItem>AAA</ComboBoxItem>
                        <ComboBoxItem>BBB</ComboBoxItem>
                    </ComboBox>
                </StackPanel>
            </Grid>
        </DataTemplate>

    </Window.Resources>

    <Grid>

        <ListBox ItemTemplate="{StaticResource myDataTemplate}">
            <ListBox.ItemsSource>
                <Specialized:StringCollection>
                    <System:String>Item 1</System:String>
                    <System:String>Item 2</System:String>
                    <System:String>Item 3</System:String> 
                </Specialized:StringCollection>
            </ListBox.ItemsSource>
        </ListBox>

    </Grid>
</Window>

Code behind hooking up to all got focus events.

using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;

namespace RoutedEventDemo
{
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();

            EventManager.RegisterClassHandler(typeof(UIElement),
                                              GotFocusEvent,
                                              new RoutedEventHandler(OnGotFocus));
        }

        private static void OnGotFocus(object sender, RoutedEventArgs e)
        {
            // Check if element that got focus is contained by a listboxitem and
            // in that case selected the listboxitem.

            DependencyObject parent = e.OriginalSource as DependencyObject;
            while (parent != null)
            {
                ListBoxItem clickedOnItem = parent as ListBoxItem;
                if (clickedOnItem != null)
                {
                    clickedOnItem.IsSelected = true;
                    return;
                }

                parent = VisualTreeHelper.GetParent(parent);
            }
        }
    }
}