On your window you should add the PreviewKeyUp event.
if the key is backspace, set handled to true.
Call RequestFocusChange()
PreviewKeyUp=Window_PreviewKeyUp
private void Window_PreviewKeyUp(object sender, System.Windows.Input.KeyEventArgs e)
{
if (e.Key==System.Windows.Input.Key.Back)
{
e.Handled = true;
RequestFocusChange(FocusNavigationDirection.Previous);
}
}
private static bool RequestFocusChange(FocusNavigationDirection direction)
{
var focused = Keyboard.FocusedElement as UIElement;
if (focused != null) return focused.MoveFocus(new TraversalRequest(direction));
return false;
}