/// <summary>
        /// Validate IR National Code
        /// </summary>
        /// <param name="nationalcode">National Code</param>
        /// <param name="lastNumber">Last Number Of National Code</param>
        /// <returns></returns>
        public static bool IsValidNationalCode(this string nationalcode, out int lastNumber)
        {
            lastNumber = -1;
            if (!nationalcode.IsItNumber()) return false;
            var invalid = new[]
                                    {
                                        "0000000000", "1111111111", "2222222222", "3333333333", "4444444444", "5555555555",
                                        "6666666666", "7777777777", "8888888888", "9999999999"
                                    };
            if (invalid.Contains(nationalcode)) return false;
            var array = nationalcode.ToCharArray();
            if (array.Length != 10) return false;
            var j = 10;
            var sum = 0;
            for (var i = 0; i < array.Length - 1; i++)
            {
                sum += Int32.Parse(array[i].ToString(CultureInfo.InvariantCulture)) * j;
                j--;
            }

            var diff = sum % 11;

            if (diff < 2)
            {
                lastNumber = diff;
                return diff == Int32.Parse(array[9].ToString(CultureInfo.InvariantCulture));
            }
            var temp = Math.Abs(diff - 11);
            lastNumber = temp;
            return temp == Int32.Parse(array[9].ToString(CultureInfo.InvariantCulture));
        }