操作身份证

 public static bool ValidIndentity(string identityNum)
        {
            if (!string.IsNullOrEmpty(identityNum) && identityNum.Length == 18)
            {
                //判断身份证是否合法
                for (int i = 0; i < 18; i++)
                {
                    if (i < 17)
                    {
                        //char类型的1对应int是49  好坑
                        int num = 0;
                        bool isNum = int.TryParse(identityNum[i].ToString(), out num);
                        if (isNum)
                        {
                            if (num > 9 || num < 0)
                            {
                                return false;
                            }
                        }
                        else
                        {
                            return false;
                        }
                    }
                    if (i == 17)
                    {
                        char[] c = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'X', 'x' };
                        if (!c.Contains(identityNum[i]))
                        {
                            return false;                            
                        }
                    }

                }

                string birth = identityNum.Substring(6, 8);
                DateTime birthDt;
                DateTime.TryParseExact(birth, "yyyyMMdd", null, System.Globalization.DateTimeStyles.None, out birthDt);
                TimeSpan ts = DateTime.Now - birthDt;
                if (ts.TotalDays / 365 > 18)
                {
                    return true;
                }
                else
                {
                    return false;
                }
            }
            else
            {
                return false;
            }
        }