public string Invoke(string firstLater) { switch (firstLater) { case "m": return(memberService.Count(null).ToString()); case "b": return(bookService.Count(null).ToString()); case "r": return(rentService.Count(a => a.isRentingCompleted == false).ToString()); case "u": return(userService.Count(null).ToString()); default: return("0"); } }