How to use a separate class to validate credit card numbers in C#
- by EvanRyan
I have set up a class to validate credit card numbers. The credit card type and number are selected on a form in a separate class. I'm trying to figure out how to get the credit card type and number that are selected in the other class (frmPayment) in to my credit card class algorithm:
public enum CardType
{
MasterCard, Visa, AmericanExpress
}
public sealed class CardValidator
{
public static string SelectedCardType { get; private set; }
public static string CardNumber { get; private set; }
private CardValidator(string selectedCardType, string cardNumber)
{
SelectedCardType = selectedCardType;
CardNumber = cardNumber;
}
public static bool Validate(CardType cardType, string cardNumber)
{
byte[] number = new byte[16];
int length = 0;
for (int i = 0; i < cardNumber.Length; i++)
{
if (char.IsDigit(cardNumber, i))
{
if (length == 16) return false;
number[length++] = byte.Parse(cardNumber[i]); //not working. find different way to parse
}
}
switch(cardType)
{
case CardType.MasterCard:
if(length != 16)
return false;
if(number[0] != 5 || number[1] == 0 || number[1] > 5)
return false;
break;
case CardType.Visa:
if(length != 16 & length != 13)
return false;
if(number[0] != 4)
return false;
break;
case CardType.AmericanExpress:
if(length != 15)
return false;
if(number[0] != 3 || (number[1] != 4 & number[1] != 7))
return false;
break;
}
// Use Luhn Algorithm to validate
int sum = 0;
for(int i = length - 1; i >= 0; i--)
{
if(i % 2 == length % 2)
{
int n = number[i] * 2;
sum += (n / 10) + (n % 10);
}
else
sum += number[i];
}
return (sum % 10 == 0);
}
}
