Random Turkish Identification Number Generator with c#

TurkishIdNoGenerator.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Samples
{
    class Program
    {
        static void Main(string[] args)
        {
            var result = TCIdGenerator();

            Console.WriteLine(result);

            Console.WriteLine("is valid : {0}",ValidTurkishIdNo(result));

            Console.WriteLine("is valid : {0}", ValidTurkishIdNo("57774200136"));
            

            Console.ReadLine();
        }

        public static string TCIdGenerator() 
        {
            string a = getRandomNumber();
            var x = a.ToCharArray();
            int[] b = new int[10];
            for (int i = 0; i < x.Length; i++)
            {
                b[i] = Convert.ToInt32(x.GetValue(i).ToString(), 10);
            }

            var c = b[0] + b[2] + b[4] + b[6] + b[8];
            var d = b[1] + b[3] + b[5] + b[7];
            var e = (7 * c - d) % 10;

            var result = a + ("" + e) + ("" + (d + c + e) % 10);

            if (!ValidTurkishIdNo(result))
                TCIdGenerator();

            return result;

        }

        private static string getRandomNumber()
        {
            Random rnd = new Random();
            var result = "" + Math.Floor(900000001 * rnd.Next() + 1e8);

            int n;
            bool isNumeric = int.TryParse(result, out n);
            if (!isNumeric || result.Substring(0, 1) == "-")
                getRandomNumber();

            return result;
        }

        public static bool ValidTurkishIdNo(string TCNo)
        {
            int[] TC = new int[11];
            for (int i = 0; i < 11; i++)
            {
                string a = TCNo[i].ToString();
                TC[i] = Convert.ToInt32(a);
            }

            int singurals = 0;
            int plurals = 0;

            for (int k = 0; k < 9; k++)
            {
                if (k % 2 == 0)
                    singurals += TC[k];
                else if (k % 2 != 0)
                    plurals += TC[k];
            }

            int t1 = (singurals * 3) + plurals;
            int c1 = (10 - (t1 % 10)) % 10;
            int t2 = c1 + plurals;
            int t3 = (t2 * 3) + singurals;
            int c2 = (10 - (t3 % 10)) % 10;

            if (c1 == TC[9] && c2 == TC[10])
                return true;
            else
                return false;
        }
    }
}