public interface IWebStoreCartManager : IServiceContractBase
{
  Cart SaveCartItem(int catalogId, int productId, int quantity);
  Cart RemoveCartItem(int catalogId, int productId);
  Cart ShowCart(int catalogId);
  Cart UpdateBillingInfo(int catalogId, Address billingInfo, bool shippingSameAsBilling);
  Cart UpdateShippingInfo(int catalogId, Address shippingInfo, bool billingSameAsShipping);
}


public class Cart
{
  public int Id { get; set; }
  public Address BillingAddress { get; set; }
  public CartItem[] CartItems { get; set;}
}

public class CartItems
{
  public int Id { get; set; }
}

public class Address
{
  public string First { get; set; }
  public string Last { get; set; }
  public string EmailAddress { get; set; }
  public string Addr1 { get; set; }
  public string Addr2 { get; set; }
  public string City { get; set; }
  public string State { get; set; }
  public string Postal { get; set; }
}