/// <summary>
/// calculates a modulus on any number, specifically
/// designed to work around the Int64 limits of the
/// current version of c# which cannot hold a number
/// larger than 9,223,372,036,854,775,807
/// </summary>
/// <param name="iban"></param>
/// <returns></returns>
private static int largeNumberModulus(string numberToModulus, int modulusOperand)
{
string modulusWorkingNumber = numberToModulus;
/// calculates a modulus on any number, specifically
/// designed to work around the Int64 limits of the
/// current version of c# which cannot hold a number
/// larger than 9,223,372,036,854,775,807
/// </summary>
/// <param name="iban"></param>
/// <returns></returns>
private static int largeNumberModulus(string numberToModulus, int modulusOperand)
{
string modulusWorkingNumber = numberToModulus;
while (modulusWorkingNumber.Length > 0 && !(modulusWorkingNumber.Length < 18 && Int64.Parse(modulusWorkingNumber) < modulusOperand))
{
// number to work with
Int64 currentNumber = 0;
if (modulusWorkingNumber.Length > 18)
{
currentNumber = Int64.Parse(modulusWorkingNumber.Substring(0, 18));
// remove first 18 characters
modulusWorkingNumber = modulusWorkingNumber.Substring(18);
}
else
{
currentNumber = Int64.Parse(modulusWorkingNumber);
// remove remaining used characters
modulusWorkingNumber = string.Empty;
}
string carryOver = (currentNumber % modulusOperand).ToString();
modulusWorkingNumber = carryOver + modulusWorkingNumber;
}
return int.Parse(modulusWorkingNumber);
}
This is part of code I mage for my shop for IBAN validation. Feel free to use if some one need.
static void Main(string[] args)
{
int modulo = 97;
string input = Reverse(“100020778788920323232343433″);
int result = 0;
int lastRowValue = 1;
for (int i = 0; i 0)
{
lastRowValue = ModuloByDigits(lastRowValue, modulo);
}
result += lastRowValue * int.Parse(input[i].ToString());
}
result = result % modulo;
Console.WriteLine(string.Format(“Result: {0}”, result));
}
public static int ModuloByDigits(int previousValue, int modulo)
{
// Calculating the modulus of a large number Wikipedia http://en.wikipedia.org/wiki/International_Bank_Account_Number
return ((previousValue * 10) % modulo);
}
public static string Reverse(string input)
{
char[] arr = input.ToCharArray();
Array.Reverse(arr);
return new string(arr);
Comment by Jaroslav Kubacek — February 11, 2010 @ 11:59 am