Example Bruter

static void Main(string[] args)
        {
            Console.WriteLine("Start Bruting...");

            String key = "11111111";

            while (true)
            {
                while (!checkLicense(key))
                {
                    int intKey = int.Parse(key);

                    if (intKey % 100 == 0)
                        Console.WriteLine("We are at key: " + key);

                    intKey += 1;
                    key = intKey.ToString();
                }

                Console.WriteLine("\n[*] Found Working: " + key);
                Console.Write("\nWanna search another one? [Y/n] ");

                if (Console.ReadLine().ToLower() == "n")
                    break;

                int intKey2 = int.Parse(key);
                intKey2 += 1;
                key = intKey2.ToString();
            }
        }

        private static bool checkLicense(String key)
        {
            if (key.Length != 8)
                return false;

            int bigNum;
            try
            {
                bigNum = int.Parse(key);
            }
            catch
            {
                return false;
            }

            if (bigNum % getInt(key, 0) != 0)
            {
                return false;
            }

            if (getInt(key, 2) + getInt(key, 5) != getInt(key, 1))
            {
                return false;
            }

            if ((getInt(key, 3) * getInt(key, 7)) % 2 != 0)
            {
                return false;
            }

            if (getInt(key, 6) - getInt(key, 5) != getInt(System.Environment.Version.ToString(), 0))
            {
                return false;
            }

            return true;
        }

        private static int getInt(String str, int pos)
        {
            return int.Parse(str.Substring(pos, 1));
        }