public IActionResult AddHotels(TourHotel model) { if (HttpContext.Session.GetString("ID") == null) { return(RedirectToAction("Login", "Admin")); } else { if (ModelState.IsValid) { int hotelID = Convert.ToInt32(model.HotelID); string tourID = model.TourID.ToString(); if (tourRepository.checkHotelID(tourID, hotelID)) { tourRepository.AddHotel(model); return(RedirectToAction("Index")); } else { ModelState.AddModelError(string.Empty, "This Hotel already exists."); //ViewBag.Error = "This Hotel already exists."; //If the system encounters an error, immediately go to the Addhotel page. //return Redirect("https://localhost:44361/Tour/AddHotel/"+tourID); TempData["Error"] = "This Hotel already exists."; return(RedirectToAction("AddHotel", "Tour", new { Id = tourID })); } } //If the system encounters an error, immediately go to the Addhotel page. return(Redirect("https://localhost:44361/Tour/AddHotel/" + model.TourID)); } }