我正在跟随MusicStore教程，已经到了教程第八部分。当我尝试添加ShoppingCart类时出现了这个错误。我尝试谷歌可能的解决方案，但没有找到一个干净的解决方案T_T..根据我的研究，我得到这个错误是因为我在教程中使用了数据库优先而不是代码优先的edmx。 我添加了这些代码并且在Add()和Remove()上遇到了错误。
namespace Project.Models
{
public partial class ShoppingCart
{
ProjectEntities db = new ProjectEntities();
string ShoppingCartId { get; set; }
public const string CartSessionKey = "cart_ID";
public static ShoppingCart GetCart(HttpContextBase context)
{
var cart = new ShoppingCart();
cart.ShoppingCartId = cart.GetCartId(context);
return cart;
}
// Helper method to simplify shopping cart calls
public static ShoppingCart GetCart(Controller controller)
{
return GetCart(controller.HttpContext);
}
public void AddToCart(Product product)
{
// Get the matching cart and album instances
var cartItem = db.Carts.SingleOrDefault(c => c.cart_ID == ShoppingCartId && c.product_ID == product.product_ID);
if (cartItem == null)
{
// Create a new cart item if no cart item exists
cartItem = new Cart
{
product_ID = product.product_ID,
cart_ID = ShoppingCartId,
Count = 1,
DateCreated = DateTime.Now
};
db.Carts.Add(cartItem);
}
else
{
// If the item does exist in the cart, then add one to the quantity
cartItem.Count++;
}
// Save changes
db.SaveChanges();
}
public int RemoveFromCart(int id)
{
// Get the cart
var cartItem = db.Carts.Single(cart => cart.cart_ID == ShoppingCartId && cart.record_ID == id);
int itemCount = 0;
if (cartItem != null)
{
if (cartItem.Count > 1)
{
cartItem.Count--;
itemCount = cartItem.Count;
}
else
{
db.Carts.Remove(cartItem);
}
// Save changes
db.SaveChanges();
}
return itemCount;
}
public void EmptyCart()
{
var cartItems = db.Carts.Where(cart => cart.cart_ID == ShoppingCartId);
foreach (var cartItem in cartItems)
{
db.Carts.Remove(cartItem);
}
// Save changes
db.SaveChanges();
}
public List<Cart> GetCartItems()
{
return db.Carts.Where(cart => cart.cart_ID == ShoppingCartId).ToList();
}
public int GetCount()
{
// Get the count of each item in the cart and sum them up
int? count = (from cartItems in db.Carts
where cartItems.cart_ID == ShoppingCartId
select (int?)cartItems.Count).Sum();
// Return 0 if all entries are null
return count ?? 0;
}
public decimal GetTotal()
{
// Multiply album price by count of that album to get
// the current price for each of those albums in the cart
// sum all album price totals to get the cart total
decimal? total = (from cartItems in db.Carts
where cartItems.cart_ID == ShoppingCartId
select (int?)cartItems.Count * cartItems.Product.Price).Sum();
return total ?? decimal.Zero;
}
public int CreateOrder(Order order)
{
decimal orderTotal = 0;
var cartItems = GetCartItems();
// Iterate over the items in the cart, adding the order details for each
foreach (var item in cartItems)
{
var orderDetail = new OrderDetail
{
product_ID = item.product_ID,
order_ID = order.order_ID,
UnitPrice = item.Product.Price,
Quantity = item.Count
};
// Set the order total of the shopping cart
orderTotal += (item.Count * item.Product.Price);
db.OrderDetails.Add(orderDetail);
}
// Set the order's total to the orderTotal count
order.Total = orderTotal;
// Save the order
db.SaveChanges();
// Empty the shopping cart
EmptyCart();
// Return the OrderId as the confirmation number
return order.order_ID;
}
// We're using HttpContextBase to allow access to cookies.
public string GetCartId(HttpContextBase context)
{
if (context.Session[CartSessionKey] == null)
{
if (!string.IsNullOrWhiteSpace(context.User.Identity.Name))
{
context.Session[CartSessionKey] = context.User.Identity.Name;
}
else
{
// Generate a new random GUID using System.Guid class
Guid tempCartId = Guid.NewGuid();
// Send tempCartId back to client as a cookie
context.Session[CartSessionKey] = tempCartId.ToString();
}
}
return context.Session[CartSessionKey].ToString();
}
// When a user has logged in, migrate their shopping cart to
// be associated with their username
public void MigrateCart(string userName)
{
var shoppingCart = db.Carts.Where(c => c.cart_ID == ShoppingCartId);
foreach (Cart item in shoppingCart)
{
item.cart_ID = userName;
}
db.SaveChanges();
}
}
}
我是MVC的初学者，希望有人能帮助我解决这个问题。
ProjectEntities类的代码。 - Pablo Claus