private void doRemoveSlides(List <SlideInfo> removedSlides)
        {
            bool wasAllowingUndo = allowUndoCreation;

            allowUndoCreation = false;
            foreach (SlideInfo slideInfo in removedSlides)
            {
                slideshow.removeSlide(slideInfo.Slide);
                if (SlideRemoved != null)
                {
                    SlideRemoved.Invoke(slideInfo.Slide);
                }
            }
            allowUndoCreation = wasAllowingUndo;
        }