MVVM and the TextBox’s SelectedText property

by

There’s no straightforward way to bind SelectedText to a data source, because it’s not a DependencyProperty… however, it quite easy to create an attached property that you could bind instead.

Here’s a basic implementation :

public static class TextBoxHelper
{

    public static string GetSelectedText(DependencyObject obj)
    {
        return (string)obj.GetValue(SelectedTextProperty);
    }

    public static void SetSelectedText(DependencyObject obj, string value)
    {
        obj.SetValue(SelectedTextProperty, value);
    }

    // Using a DependencyProperty as the backing store for SelectedText.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty SelectedTextProperty =
        DependencyProperty.RegisterAttached(
            "SelectedText",
            typeof(string),
            typeof(TextBoxHelper),
            new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, SelectedTextChanged));

    private static void SelectedTextChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
    {
        TextBox tb = obj as TextBox;
        if (tb != null)
        {
            if (e.OldValue == null && e.NewValue != null)
            {
                tb.SelectionChanged += tb_SelectionChanged;
            }
            else if (e.OldValue != null && e.NewValue == null)
            {
                tb.SelectionChanged -= tb_SelectionChanged;
            }

            string newValue = e.NewValue as string;

            if (newValue != null && newValue != tb.SelectedText)
            {
                tb.SelectedText = newValue as string;
            }
        }
    }

    static void tb_SelectionChanged(object sender, RoutedEventArgs e)
    {
        TextBox tb = sender as TextBox;
        if (tb != null)
        {
            SetSelectedText(tb, tb.SelectedText);
        }
    }

}

You can then use it like that in XAML :

<TextBox Text="{Binding Message}" u:TextBoxHelper.SelectedText="{Binding SelectedText}" />

More Related Contents:

  1. Set focus on TextBox in WPF from view model
  2. INotifyPropertyChanged vs. DependencyProperty in ViewModel
  3. How to define TextBox input restrictions?
  4. Firing a double click event from a WPF ListView item using MVVM
  5. What is a ViewModelLocator and what are its pros/cons compared to DataTemplates?
  6. Any way to make a WPF textblock selectable?
  7. WPF: simple TextBox data binding
  8. Passing parameters between viewmodels
  9. Why MVVM and what are it’s core benefits? [duplicate]
  10. How to change disabled background color of TextBox in WPF
  11. AutoComplete TextBox in WPF
  12. Keyboard events in a WPF MVVM application?
  13. How to open a new window using MVVM Light Toolkit
  14. Grouping items in a ComboBox
  15. KeyBinding in UserControl doesn’t work when TextBox has the focus
  16. WPF Grid as ItemsPanel for a list dynamically bound to an ItemsControl
  17. Set the caret/cursor position to the end of the string value WPF textbox
  18. How have you successfully implemented MessageBox.Show() functionality in MVVM?
  19. How can I Have a WPF EventTrigger on a View trigger when the underlying Viewmodel dictates it should?
  20. How to make all controls resize accordingly proportionally when window is maximized?
  21. WPF: How to programmatically remove focus from a TextBox
  22. Weird problem where Button does not get re-enabled unless the mouse is clicked
  23. How can I sort a ListBox using only XAML and no code-behind?
  24. InputBindings work only when focused
  25. Is MVVM pattern broken?
  26. Keybinding a RelayCommand
  27. MVVM pattern violation: MediaElement.Play()
  28. Why isn’t TextBox.Text in WPF animatable?
  29. What exactly are “WPF services”?
  30. How can I tell my DataTemplate to bind to a property in the PARENT ViewModel?

Leave a Comment