货币是否是价值对象

public class Person 
{
    private int id;
    private readonly PersonID personID;

    private readonly string email;
    private readonly string firstName;
    private readonly string lastName;

    private readonly string username;
    private readonly string password;
    private readonly Address BillingAddress;
}

public class Currency : IValueObject<Currency>
{
    private string name;
    private string currencyCode;
    private decimal rate;
    private string displayLocale;
    private string customFormatting;
    private int displayOrder;
    private bool primaryExchangeRateCurrency;
    private bool primaryStoreCurrency;

    //<summary>
    //Gets or a value indicating whether the currency is primary exchange rate currency
    //</summary>

    public bool IsPrimaryExchangeRateCurrency
    {
       get
       {
           return primaryExchangeRateCurrency;
       }
    }

   /// <summary>
    /// Gets or a value indicating whether the currency is primary store currency
    /// </summary>

    public bool IsPrimaryStoreCurrency
    {
         get
         {
                return primaryStoreCurrency;
         }
    }
}