/// <summary>
/// Validates the passed-in card, making sure that the card is not expired
/// and that it passed the Luhn Algorigthm
/// </summary>
/// <param name="card">The Credit Card to validate</param>
public bool IsValid()
{
bool isValid = false;
isValid = Expiration >= DateTime.Today;
if (isValid)
{
//string empty cars, and set to an array
char[] cardChars = AccountNumber.Replace(" ", "").ToCharArray();
int sum = 0;
int currentDigit = 0;
bool alternate = false;
//use the Luhn Algorithm to validate the card number
//http://en.wikipedia.org/wiki/Luhn_algorithm
//count from left to right
for (int i = cardChars.Length - 1; i >= 0; i--)
{
if (alternate)
{
if (int.TryParse(cardChars[i].ToString(), out currentDigit))
{
currentDigit *= 2;
if (currentDigit > 9)
{
currentDigit -= 9;
}
}
else
{
// non-int character
return(false);
}
}
sum += currentDigit;
alternate = !alternate;
}
isValid = sum % 10 == 0;
}
return(isValid);
}
