如何在 C# 中使用单独的类来验证信用卡号码

Question

我已经设置了一个类来验证信用卡号。信用卡类型和号码是在单独类别的表格上选择的。我试图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

您错过了获得更好的 OOP 和更清晰的代码的绝佳机会。

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();
   }
}

Answer 2

对于初学者来说，我会使用正则表达式进行简单的验证（所有数字，特定长度）。

但就你的问题而言，我不确定我是否理解问题所在。从您在这里发布的内容来看，您似乎应该删除构造函数并将整个内容设为静态类。

public enum CardType
{
    MasterCard,
    Visa,
    AmericanExpress,
}

public static class CardValidator
{
    public static bool Validate(CardType cardType, string cardNumber)
    {
        string strippedCardNumber = Regex.Replace(cardNumber, @"\D", String.Empty);


        ICardValidator validator = SelectCardValidator(cardType);

        return validator.Validate(strippedCardNumber);
    }

    private static ICardValidator SelectCardValidator(CardType cardType)
    {
        switch (cardType)
        {
            case CardType.MasterCard:
                return new MasterCardValidator();
            case CardType.Visa:
                return new VisaValidator();
            case CardType.AmericanExpress:
                return new AmericanExpressValidator();
            default:
                return new UnknownCardTypeValidator();
        }
    }

    private interface ICardValidator
    {
        bool Validate(string cardNumber);
    }

    private class UnknownCardTypeValidator : ICardValidator
    {
        #region ICardValidator Members

        public bool Validate(string cardNumber)
        {
            return false;
        }

        #endregion
    }

    private abstract class LuhnAlgorithmValidator : ICardValidator
    {

        #region ICardValidator Members

        public virtual bool Validate(string cardNumber)
        {
            // Implement Luhn Algorithm here

            return false;
        }

        #endregion
    }

    private class MasterCardValidator : LuhnAlgorithmValidator
    {
        public override bool Validate(string cardNumber)
        {
            bool isValid = false; // replace with MasterCard validation
            return isValid && base.Validate(cardNumber);
        }
    }

    private class VisaValidator : LuhnAlgorithmValidator
    {
        public override bool Validate(string cardNumber)
        {
            bool isValid = false; // replace with Visa validation
            return isValid && base.Validate(cardNumber);
        }
    }

    private class AmericanExpressValidator : LuhnAlgorithmValidator
    {
        public override bool Validate(string cardNumber)
        {
            bool isValid = false; // replace with AmEx validation
            return isValid && base.Validate(cardNumber);
        }
    }
}

Answer 3

在 frmPayments btnValidate_click （或类似）事件处理程序中，只需调用 CardValidator.Validate 方法。

但是，CardValidator 构造函数具有参数，即使它是私有的，并且从未被调用？为什么要向类添加属性？

编辑：错过了示例代码的一些部分。