public ChangeShelfNumberStatusCodes ChangeShelfNumber(int shelfID, int shelfNumber) { var currentShelf = shelfManager.GetShelfByShelfId(shelfID); if (currentShelf == null) { return(ChangeShelfNumberStatusCodes.NoSuchShelf); } if (currentShelf.ShelfNumber == shelfNumber) { return(ChangeShelfNumberStatusCodes.CanNotChangeToSameNumber); } shelfManager.ChangeShelfNumber(shelfID, shelfNumber); return(ChangeShelfNumberStatusCodes.Ok); }