internal void DeleteAnchor(Data.Anchor anchor)
 {
     anchor.IsSelected = false;
     U.RemoveFromArray(ref Anchors, anchor);
     KeysAndAnchors.Remove(anchor);
 }
 internal void AddAnchor(Data.Anchor anchor)
 {
     anchor.IsSelected = true;
     U.AddToArray(ref Anchors, anchor);
     KeysAndAnchors.Add(anchor);
 }