private void DeleteTree()
        {
            Baum baumToDelete = BaumCollection.Where(x => x.IsMarked == true).FirstOrDefault();

            if (baumToDelete != null)
            {
                BaumCollection.Remove(baumToDelete);
            }
            else
            {
            }
        }
        private void MoveTree(PointerPoint imagePoint, PointerPoint canvasPoint)
        {
            if (BaumCollection != null)
            {
                Baum selectedTree = (Baum)BaumCollection.Where(x => x.IsMarked == true).FirstOrDefault();

                if (selectedTree != null)
                {
                    selectedTree.CanvasPosition = canvasPoint.Position;
                    selectedTree.ImagePosition  = imagePoint.Position;

                    BaumCollection.Remove(selectedTree);
                    BaumCollection.Add(selectedTree);
                }
            }
        }