Inline editing TextBlock in a ListBox with Data Template (WPF)

Question

Using WPF, I have a ListBox control with a datatemplate inside it. The relevant XAML code is shown below:

<ListBox Name="_todoList" Grid.Row="1" BorderThickness="2"
     Drop="todoList_Drop" AllowDrop="True"
     HorizontalContentAlignment="Stretch"
     ScrollViewer.HorizontalScrollBarVisibility="Disabled"                 
     AlternationCount="2">
     <ListBox.ItemTemplate>
         <DataTemplate>
             <Grid Margin="4">
                 <Grid.ColumnDefinitions>
                     <ColumnDefinition Width="Auto" />
                     <ColumnDefinition Width="*" />
                 </Grid.ColumnDefinitions>
                 <CheckBox Grid.Column="0" Checked="CheckBox_Check" />
                 <TextBlock Name="descriptionBlock"
                            Grid.Column="1"
                            Text="{Binding Description}"
                            Cursor="Hand" FontSize="14"
                            ToolTip="{Binding Description}"
                            MouseDown="TextBlock_MouseDown" />                      
             </Grid>
         </DataTemplate>
     </ListBox.ItemTemplate>
</ListBox>

What I am trying to do is make the TextBlock respond to a (double)click which turns it into a TextBox. The user can then edit the description, and press return or change focus to make the change. I have tried adding a TextBox element in the same position as the TextBlock and making its visiblity 'collapsed', but I don't know how to navigate to the right TextBox when the user has clicked on a TextBlock. That is, I know the user has clicked on a certain TextBlock, now which TextBox do I show?

Any help would be appreciated greatly,

-Ko9

Answer 1

The ideal way to do this would be to create a ClickEditableTextBlock control, which by default renders as a TextBlock but shows a TextBox when the user clicks it. Because any given ClickEditableTextBlock has only one TextBlock and one TextBox, you don't have the matching issue. Then you use a ClickEditableTextBlock instead of separate TextBlocks and TextBoxes in your DataTemplate.

This has the side benefit of encapsulating the functionality in a control so you don't pollute your main window code-behind with the edit behaviour, plus you can easily reuse it in other templates.

---

If this sounds like too much effort, you can use Tag or an attached property to associate each TextBlock with a TextBox:

<DataTemplate>
  <StackPanel>
    <TextBlock Text="whatever"
               MouseDown="TextBlock_MouseDown"
               Tag="{Binding ElementName=tb}" />
    <TextBox Name="tb" />
  </StackPanel>
</DataTemplate>

Note the use of {Binding ElementName=tb} on the Tag to refer to the TextBox named tb.

And in your code-behind:

private void TextBlock_MouseDown(object sender, MouseButtonEventArgs e)
{
  FrameworkElement textBlock = (FrameworkElement)sender;
  TextBox editBox = (TextBox)(textBlock.Tag);
  editBox.Text = "Wow!";  // or set visible or whatever
}

(To avoid the use of the nasty Tag property, you could define a custom attached property to carry the TextBox binding, but for brevity I'm not showing that.)

Answer 2

What I've done in these situations is used the XAML hierarchy to determine which element to show/hide. Something along the lines of:

<Grid>
  <TextBlock MouseDown="txtblk_MouseDown" />
  <TextBox LostFocus="txtbox_LostFocus" Visibility="Collapsed" />
</Grid>

with the code:

protected void txtblk_MouseDown(object sender, MouseButtonEventArgs e)
{
    TextBox txt = (TextBox)((Grid)((TextBlock)sender).Parent).Children[1];
    txt.Visibility = Visibility.Visible;
    ((TextBlock)sender).Visibility = Visibility.Collapsed;
}

protected void txtbox_LostFocus(object sender, RoutedEventArgs e)
{
    TextBlock tb = (TextBlock)((Grid)((TextBox)sender).Parent).Children[0];
    tb.Text = ((TextBox)sender).Text;
    tb.Visibility = Visibility.Visible;
    ((TextBox)sender).Visibility = Visibility.Collapsed;
}

I always turn stuff like this that I'm going to reuse into a UserControl, which I can add additional error handling to, and guarantee that the Grid will only contain two items, and the order of them will never change.

EDIT: Additionally, turning this into a UserControl allows you to create a Text property for each instantiation, so you can name each one and reference the text directly without fishing for the current value through the ((TextBox)myGrid.Children[1]).Text casting. This will make your code much more efficient and clean. If you make it into a UserControl, you can also name the TextBlock and TextBox elements, so no casting is needed at all.