Update

Author: ngtduc693

Algorithms/Other/Luhn.cs

@@ -28,8 +28,8 @@ public static class Luhn
     /// <returns>Missing digit.</returns>
     public static int GetLostNum(string number)
     {
-        var missingDigitIndex = number.Length - 1 - number.LastIndexOf('x');
-        var checkDigit = GetSum(number.Replace("x", "0")) * 9 % 10;
+        var missingDigitIndex = number.Length - 1 - number.LastIndexOf("x", StringComparison.CurrentCultureIgnoreCase);
+        var checkDigit = GetSum(number.Replace("x", "0", StringComparison.CurrentCultureIgnoreCase)) * 9 % 10;
 
         return missingDigitIndex % 2 == 0
             ? checkDigit