Validera kreditkortsnummer med Luhn's algoritm

private static bool ValidateCardNumber(string cardNumber)
{
try
{
// Array to contain individual numbers
System.Collections.ArrayList CheckNumbers = new ArrayList();
// So, get length of card
int CardLength = cardNumber.Length;

// Double the value of alternate digits, starting with the second digit
// from the right, i.e. back to front.
// Loop through starting at the end
for (int i = CardLength - 2; i >= 0; i = i - 2)
{
// Now read the contents at each index, this
// can then be stored as an array of integers

// Double the number returned
CheckNumbers.Add(Int32.Parse(cardNumber[i].ToString()) * 2);
}

int CheckSum = 0; // Will hold the total sum of all checksum digits

// Second stage, add separate digits of all products
for (int iCount = 0; iCount <= CheckNumbers.Count - 1; iCount++)
{
int _count = 0; // will hold the sum of the digits

// determine if current number has more than one digit
if ((int)CheckNumbers[iCount] > 9)
{
int _numLength = ((int)CheckNumbers[iCount]).ToString().Length;
// add count to each digit
for (int x = 0; x < _numLength; x++)
{
_count = _count + Int32.Parse(
((int)CheckNumbers[iCount]).ToString()[x].ToString());
}
}
else
{
// single digit, just add it by itself
_count = (int)CheckNumbers[iCount];
}
CheckSum = CheckSum + _count; // add sum to the total sum
}
// Stage 3, add the unaffected digits
// Add all the digits that we didn't double still starting from the
// right but this time we'll start from the rightmost number with
// alternating digits
int OriginalSum = 0;
for (int y = CardLength - 1; y >= 0; y = y - 2)
{
OriginalSum = OriginalSum + Int32.Parse(cardNumber[y].ToString());
}

// Perform the final calculation, if the sum Mod 10 results in 0 then
// it's valid, otherwise its false.
return (((OriginalSum + CheckSum) % 10) == 0);
}
catch
{
return false;
}
}