protected override void OnSelectionChanging(InkCanvasSelectionChangingEventArgs e) {
bool selBak = Keyboard.Modifiers == ModifierKeys.Control;
ReadOnlyCollection<UIElement> col = e.GetSelectedElements();
List<UIElement> rez = new List<UIElement>();
foreach (UIElement el in col)
if (selBak && el == bkg)
rez.Add(el);
else if (!selBak && el != bkg)
rez.Add(el);
e.SetSelectedElements(rez);
}
private void selectingText(object sender, InkCanvasSelectionChangingEventArgs e)
{
e.SetSelectedElements(filterMyText(e.GetSelectedElements()));
}