按值传送一个结构
using System;
public struct CreditCard
{
double cardNumeber;
DateTime expiryDate; public double CardNumber
   {
     get
       {
         return cardNumber;
        }
     set
      {
       cardNumber=value;
        }
    }
 public DataTime ExpiryDate
  { 
  get
    { 
    return expiryDate;
     }
  set
    {
     expiryDate=value;
   }
  }
}public class Authorization
  {
  public static decimal GetBalance(CreditCard creditCard)
   {
    creditCard.ExpiryDate=creditCard.ExpiryDate.AddMonths(12);
    return(decimal)845.21;
   }
  }     这段看不懂,能给解释一下吗    
class Payments
{
 static void Main()
  {
   CreditCard card =new CreditCard();
    Decimal balance;
   card.CardNumber=1111222333444;
   card.ExpitryDate=Convert.ToDateTime("01/03/2003");   balance=Authorization.GetBalance(card);
       这句也看不懂   Console.WriteLine("Card Number-"+card.CardNumber);
   Console.WriteLine(Expiry Date-"+card.Expiry.ToShortDateString());
   Console.WriteLine("Balance-"+balance);
 }
}