public async Task <SerialsDB> Add(string newSerial) { var existingSerial = _serialService.GetSerialBySerial(newSerial); if (existingSerial.Id != 0) { int id = _serialService.GetLastIdSerial().Result; var serial = new SerialsDB { Id = id + 1, Serial = newSerial }; var result = await _context.Serials.AddAsync(serial); return(result.Entity); } return(new SerialsDB { }); }