【求助】信用卡验证算法

int total = 0;
            int temp = 0;
            char[] ccDigits = cardNumber.ToCharArray();
            for (int i = 0; i < cardNumber.Length; i++)
            {
                if (((i + 1) % 2) == 0)
                {
                    total += int.Parse(ccDigits[i].ToString());
                }
                else
                {
                    temp = int.Parse(ccDigits[i].ToString()) * 2;
                    if (temp > 9)
                    {
                        temp = (int)temp - 9;
                    }
                    total += temp;
                }
            }
            if ((total % 10) == 0)
            {
                return true;
            }
            else
            {
                return false;
            }