public IActionResult Create(Office model) { if (HttpContext.Session.GetString("ID") == null) { return(RedirectToAction("Login", "Admin")); } else { if (ModelState.IsValid) { bool check = officeRepository.checkID(model.ID); if (check) { officeRepository.Add(model); return(RedirectToAction("Index")); } else { ViewBag.listAllCities = officeRepository.listAllCities(); ModelState.AddModelError(string.Empty, "This ID already exists."); return(View()); } } ViewBag.listAllCities = officeRepository.listAllCities(); return(View(model)); } }