public ActionResult <string> Gateway([FromBody] GatewayModel gateway) { string result = "error"; try { DevicesRepository devices = new DevicesRepository(_options); if (devices.GetDeviceBySerial(gateway.Serial).Count == 0) { result = devices.InsertGateway(gateway.Serial, gateway.Brand, gateway.Ip, gateway.Port); } else { result = "The serial number entered was already registered. Please check the serial number."; } } catch (Exception ex) { return(ex.Message); } return(result); }