private void AlignVertically(VerticalAlignment alignment)
 {
     var aligner = new Aligner(DesignSurface.SelectedItems.Cast<ICanvasItem>().ToList());
     aligner.AlignVertically(alignment);
 }
 private void AlignHorizontally(HorizontalAlignment alignment)
 {
     var aligner = new Aligner(DesignSurface.GetSelectedCanvasItems());
     aligner.AlignHorizontally(alignment);
 }