储蓄List< CartItem>到ASP.NET中的会话

CartItems保存在SQL数据库中。

我想把所有的CartItems放到List中，并转移到Instance.Items.

实例变量被保存到会话中。

代码如下:

public class ShoppingCart
{
    public List<CartItem> Items { get; private set; }
    public static SqlConnection conn = new SqlConnection(connStr.connString);
    public static readonly ShoppingCart Instance;
    static ShoppingCart()
    {
        if (HttpContext.Current.Session["ASPNETShoppingCart"] == null)
        {
                Instance = new ShoppingCart();
                Instance.Items = new List<CartItem>();
                HttpContext.Current.Session["ASPNETShoppingCart"] = Instance;  
        }
        else
        {
            Instance = (ShoppingCart)HttpContext.Current.Session["ASPNETShoppingCart"];
        }
    }

返回List的代码。我想保存从这个函数返回的List到Instance.Items。这样可以保存到会话中。

    public static List<CartItem> loadCart(String CustomerId)
    {
        String sql = "Select * from Cart where CustomerId='" + CustomerId + "'";
        SqlCommand cmd = new SqlCommand(sql, conn);
        List<CartItem> lstCart = new List<CartItem>();
        try
        {
            conn.Open();
            SqlDataReader reader = cmd.ExecuteReader();
            while (reader.Read())
            {
                CartItem itm = new CartItem(Convert.ToInt32(reader["ProductId"].ToString()));
                itm.Quantity = Convert.ToInt32(reader["Quantity"].ToString());
                lstCart.Add(itm);
            }
        }
        catch (Exception ex)
        { }
        finally
        {
            conn.Close();
        }
        return lstCart;
    }

public class ShoppingCart
{
    public List<CartItem> Items { get; private set; }
    public static SqlConnection conn = new SqlConnection(connStr.connString);
    public static readonly ShoppingCart Instance;
    static ShoppingCart RetrieveShoppingCart()
    {
        if (HttpContext.Current.Session["ASPNETShoppingCart"] == null)
        {
                Instance = new ShoppingCart();
                Instance.Items = new List<CartItem>();
                HttpContext.Current.Session["ASPNETShoppingCart"] = Instance;  
        }
        else
        {
            Instance = (ShoppingCart)HttpContext.Current.Session["ASPNETShoppingCart"];
        }
        return Instance;
    }
}