How to keep WPF TextBox selection when not focused?

Question

I want to show a selection in a WPF TextBox even when it's not in focus. How can I do this?

Conserve

Answer 1

I have used this solution for a RichTextBox, but I assume it will also work for a standard text box. Basically, you need to handle the LostFocus event and mark it as handled.

  protected void MyTextBox_LostFocus(object sender, RoutedEventArgs e)
  {    
     // When the RichTextBox loses focus the user can no longer see the selection.
     // This is a hack to make the RichTextBox think it did not lose focus.
     e.Handled = true;
  }

The TextBox will not realize it lost the focus and will still show the highlighted selection.

I'm not using data binding in this case, so it may be possible that this will mess up the two way binding. You may have to force binding in your LostFocus event handler. Something like this:

     Binding binding = BindingOperations.GetBinding(this, TextProperty);
     if (binding.UpdateSourceTrigger == UpdateSourceTrigger.Default ||
         binding.UpdateSourceTrigger == UpdateSourceTrigger.LostFocus)
     {
        BindingOperations.GetBindingExpression(this, TextProperty).UpdateSource();
     }

Downy

+1 Nice solution - helped me with creating a search feature... Thx – Tergal

This mostly works, but breaks scrolling on non-focused RichTextBoxes with selections in them -- the selection highlight doesn't move with the text. – Durant

Better answer below – Eulogistic

this won't work if you never go into the textbox. If the selection is set before presenting the textbox, or the selection is changed somewhere else in the program, what do you have to do to show the selection when the textbox is inactive? – Barometrograph

In a multiline textbox this won't work, it won't scroll the selection with the text. – Lodi

Answer 2

TextBoxBase.IsInactiveSelectionHighlightEnabled Property has available since .NET Framework 4.5

public bool IsInactiveSelectionHighlightEnabled { get; set; }

Dorton

Two notes: (1) the inactive highlight is applied when focus is lost, so if the field never had focus, it won't appear. Important when you're setting the selection programmatically. (2) The default color for SystemColors.InactiveSelectionHighlightBrushKey is a barely-noticeable dim grey, so changing that to something more colorful is recommended. – Gault

In .NET 4 you can use the SelectionBrush property of the textbox. When you set it to for instance Brushes.Yellow you get a selection that is still well visible as an inactive selection. – Lodi

Answer 3

Another option is to define a separate focus scope in XAML to maintain the selection in the first TextBox.

<Grid>
  <Grid.RowDefinitions>
    <RowDefinition/>
    <RowDefinition/>
  </Grid.RowDefinitions>

  <TextBox Grid.Row="0" Text="Text that does not loose selection."/>
  <StackPanel Grid.Row="1" FocusManager.IsFocusScope="True">
    <TextBox Text="Some more text here." />
    <Button  Content="Run" />
    <Button Content="Review" />
  </StackPanel>
</Grid>

Gazette

There's a good visual demonstration of this at wpfhacks.blogspot.com/2009/06/… – Introjection

This solution is more to my convenience. – Rolo

Answer 4

public class CustomRichTextBox : RichTextBox
{
     protected override void OnLostFocus(RoutedEventArgs e)
     {

     }
}

Alric

Answer 5

I found that the suggestions listed (add a LostFocus handler, defining a FocusScope) to not work, but I did come across the code listed here: http://naracea.com/2011/06/26/selection-highlight-and-focus-on-wpf-textbox/, which creates a custom Adorner that highlights the text when not focused.

Wintergreen

The link is broken; it is now at jiribrossmann.com/projects/naracea/2011/06/26/… . – Accouterment