18位號碼：

 1   private static bool CheckIDCard18(string Id)
 2         {
 3             long n = 0;
 4             if (long.TryParse(Id.Remove(17), out n) == false || n < Math.Pow(10, 16) || long.TryParse(Id.Replace(‘x‘, ‘0‘).Replace(‘X‘, ‘0‘), out n) == false)
 5             {
 6
 
                 return false;
 7             }
 8             string address = "11x22x35x44x53x12x23x36x45x54x13x31x37x46x61x14x32x41x50x62x15x33x42x51x63x21x34x43x52x64x65x71x81x82x91";
 9             if (address.IndexOf(Id.Remove(2)) == -1)
10             {
11                 return false;
12
 
             }
13             string birth = Id.Substring(6, 8).Insert(6, "-").Insert(4, "-");
14             DateTime time = new DateTime();
15             if (DateTime.TryParse(birth, out time) == false)
16             {
17                 return false;
18             }
19             string
 
[] arrVarifyCode = ("1,0,x,9,8,7,6,5,4,3,2").Split(‘,‘);
20             string[] Wi = ("7,9,10,5,8,4,2,1,6,3,7,9,10,5,8,4,2").Split(‘,‘);
21             char[] Ai = Id.Remove(17).ToCharArray();
22             int sum = 0;
23             for (int i = 0; i < 17; i++)
24             {
25                 sum += int.Parse(Wi[i]) * int.Parse(Ai[i].ToString());
26             }
27             int y = -1;
28             Math.DivRem(sum, 11, out y);
29             if (arrVarifyCode[y] != Id.Substring(17, 1).ToLower())
30             {
31                 return false;
32             }
33             return true;//正確
34         }

15位號碼：

   private static bool CheckIDCard15(string Id)
        {
            long n = 0;
            if (long.TryParse(Id, out n) == false || n < Math.Pow(10, 14))
            {
                return false;
            }
            string address = "11x22x35x44x53x12x23x36x45x54x13x31x37x46x61x14x32x41x50x62x15x33x42x51x63x21x34x43x52x64x65x71x81x82x91";
            if (address.IndexOf(Id.Remove(2)) == -1)
            {
                return false;
            }
            string birth = Id.Substring(6, 6).Insert(4, "-").Insert(2, "-");
            DateTime time = new DateTime();
            if (DateTime.TryParse(birth, out time) == false)
            {
                return false;
            }
            return true;//正確
        }   

C#驗證身份證號碼正確性