MVVM and the TextBox's SelectedText property

Question

I have a TextBox with a ContextMenu in it. When the user right clicks inside the TextBox and chooses the appropriate MenuItem, I would like to grab the SelectedText in my v

Answer 1

I know it's been answered and accepted, but I thought I would add my solution. I use a Behavior to bridge between the view model and the TextBox. The behavior has a dependency property (CaretPositionProperty) which can be bound two way to the view model. Internally the behavior deals with the updates to/from the TextBox.

public class SetCaretIndexBehavior : Behavior
    {
        public static readonly DependencyProperty CaretPositionProperty;
        private bool _internalChange;

    static SetCaretIndexBehavior()
    {

    CaretPositionProperty = DependencyProperty.Register("CaretPosition", typeof(int), typeof(SetCaretIndexBehavior), new PropertyMetadata(0, OnCaretPositionChanged));
}

public int CaretPosition
{
    get { return Convert.ToInt32(GetValue(CaretPositionProperty)); }
    set { SetValue(CaretPositionProperty, value); }
}

protected override void OnAttached()
{
    base.OnAttached();
    AssociatedObject.KeyUp += OnKeyUp;
}

private static void OnCaretPositionChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    var behavior = (SetCaretIndexBehavior)d;
    if (!behavior._internalChange)
    {
        behavior.AssociatedObject.CaretIndex = Convert.ToInt32(e.NewValue);
    }
}

    private void OnKeyUp(object sender, KeyEventArgs e)
    {
        _internalChange = true;
        CaretPosition = AssociatedObject.CaretIndex;
        _internalChange = false;
    }
}