Data commit

Task/Validate-International-Securities-Identification-Number/C-sharp/validate-international-securities-identification-number.cs

@@ -0,0 +1,51 @@
+using System;
+using System.Linq;
+using System.Text.RegularExpressions;
+
+namespace ValidateIsin
+{
+    public static class IsinValidator
+    {
+        public static bool IsValidIsin(string isin) =>
+            IsinRegex.IsMatch(isin) && LuhnTest(Digitize(isin));
+
+        private static readonly Regex IsinRegex =
+            new Regex("^[A-Z]{2}[A-Z0-9]{9}\\d$", RegexOptions.Compiled);
+
+        private static string Digitize(string isin) =>
+            string.Join("", isin.Select(c => $"{DigitValue(c)}"));
+
+        private static bool LuhnTest(string number) =>
+            number.Reverse().Select(DigitValue).Select(Summand).Sum() % 10 == 0;
+
+        private static int Summand(int digit, int i) =>
+            digit + (i % 2) * (digit - digit / 5 * 9);
+
+        private static int DigitValue(char c) =>
+            c >= '0' && c <= '9'
+                ? c - '0'
+                : c - 'A' + 10;
+   }
+	
+   public class Program
+   {
+        public static void Main()
+        {
+            string[] isins =
+            {
+                "US0378331005",
+                "US0373831005",
+                "U50378331005",
+                "US03378331005",
+                "AU0000XVGZA3",
+                "AU0000VXGZA3",
+                "FR0000988040"
+            };
+
+            foreach (string isin in isins) {
+                string validOrNot = IsinValidator.IsValidIsin(isin) ? "valid" : "not valid";
+                Console.WriteLine($"{isin} is {validOrNot}");
+            }
+        }
+    }
+}