public UpdateResult UpdateCityIfChanged() {
    if (Id > 0) {
        bool isActive = db.IsPersonActive(Id);
        if (isActive) {
            if (FirstName != null && LastName != null) {
                string normalizedFirstName = FirstName.ToUpper();
                string normalizedLastName = LastName.ToUpper();
                string currentCity = db.GetCurrentCityByName(
                    normalizedFirstName, normalizedLastName);
                if (currentCity != City) {
                    bool success = db.UpdateCurrentCity(Id, City);
                    if (success) {
                        return UpdateResult.Success;
                    } else {
                        return UpdateResult.UpdateFailed;
                    }
                } else {
                    return UpdateResult.CityDidNotChange;
                }
            } else {
                return UpdateResult.InvalidName;
            }
        } else {
            return UpdateResult.PersonInactive;
        }
    } else {
        return UpdateResult.InvalidId;
    }
}