c# - 如何使用单独的类在 C# 中验证信用卡号

Question

我已经设置了一个类来验证信用卡号。信用卡类型和号码在单独类别的表格上选择。我正在尝试弄清楚如何将在其他类 (frmPayment) 中选择的信用卡类型和号码添加到我的信用卡类算法中:

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);

}

Answer 1

您正在错失更好的 OOP 和更简洁的代码的绝佳机会。

class CreditCard
{
   public CreditCard(string number, string expiration, string cvv2) {...}

   public virtual bool IsValid()
   {
       /* put common validation logic here */
   }

   /* factory for actual cards */
   public static CreditCard GetCardByType (CardType card, string number, string expiration, string cvv2)
   {
        switch (card)
        {
             case  CardType.Visa:
                  return new VisaCreditCard(...);

             ...
        }
   }
}

class VisaCreditCard : CreditCard
{
   public VisaCreditCard (string number, string expiration, string cvv2 )
      : base (number, expiration, cvv2)
   {...}

   public override bool IsValid()
   {
       /* check Visa rules... */
       bool isValid = ...

       return isValid & base.IsValid();
   }
}