C#身份证验证小例子

 private string CheckCidInfo(string cid)
            double iSum = 0;
            System.Text.RegularExpressions.Regex rg = new System.Text.RegularExpressions.Regex(@"^\d{17}(\d|x)$");
            System.Text.RegularExpressions.Match mc = rg.Match(cid);
            if (!mc.Success)
            {
                return "";
            }
            cid = cid.ToLower();
            cid = cid.Replace("x", "a");
            if (aCity[int.Parse(cid.Substring(0, 2))] == null)
            {
                return "地区";
            }
            try
            {
                DateTime.Parse(cid.Substring(6, 4) + "-" + cid.Substring(10, 2) + "-" + cid.Substring(12, 2));
            }
            catch
            {
                return "生日";
            }
            for (int i = 17; i >= 0; i--)
            {
                iSum += (System.Math.Pow(2, i) % 11) * int.Parse(cid[17 - i].ToString(), System.Globalization.NumberStyles.HexNumber);
            }
            if (iSum % 11 != 1)
            {
                return ("证号");
            }

            return (aCity[int.Parse(cid.Substring(0, 2))] + "," + cid.Substring(6, 4) + "-" + cid.Substring(10, 2) + "-" + cid.Substring(12, 2) + "," + (int.Parse(cid.Substring(16, 1)) % 2 == 1 ? "男" : "女"));

        }