internal override void Dispose(bool disposing)
        {
            if (_cells != null)
            {
                _cells.Dispose();
                _cells = null;
            }

            if (_columns != null)
            {
                _columns.Dispose();
                _columns = null;
            }

            if (_pictures != null)
            {
                _pictures.Dispose();
                _pictures = null;
            }

            if (_shapes != null)
            {
                _shapes.Dispose();
                _shapes = null;
            }

            if (_rows != null)
            {
                _rows.Dispose();
                _rows = null;
            }

            if (_pageSetup != null)
            {
                _pageSetup.Dispose();
                _shapes = null;
            }

            if (_chartobjects != null)
            {
                _chartobjects.Dispose();
                _chartobjects = null;
            }

            if (_hyperlinks != null)
            {
                _hyperlinks.Dispose();
                _hyperlinks = null;
            }

            base.Dispose(disposing);
        }