internal void RemoveAdorner(CanvasAdorner adorner)
{
if (adorner == null) throw new ArgumentNullException(nameof(adorner));
if (adorner.ParentCanvas != this) throw new InvalidOperationException("Invalid ParentCanvas.");
adorner.SetCanvas(null);
adornerCanvas.Children.Remove(adorner);
}
internal void AddAdorner(CanvasAdorner adorner)
{
if (adorner == null) throw new ArgumentNullException(nameof(adorner));
adorner.SetCanvas(this);
adornerCanvas.Children.Add(adorner);
}