求解释一个蛋疼的bug

        private List<EShop_UserSell> AddUserSell(EShop_Order order, IEnumerable<EShop_OrderDetails> list)
        {
            List<EShop_UserSell> rtnList = new List<EShop_UserSell>();
            foreach (var d in list)
            {
                EShop_UserSell usersell = new EShop_UserSell();
                usersell.EShopOrder_OrderCode = d.EShopOrderCode;
                usersell.Erp_ColorID = d.Erp_ColorID;
                usersell.Erp_SizeID = d.Erp_SizeID;
                usersell.ProducPicUrl = d.EShopOrderDetails_ProducPicUrl;
                usersell.ProductHTML_Code = d.Product_Code;
                usersell.ProductHTML_FormatShowName = d.EShopOrderDetails_ProductName;
                usersell.Sell_AddDate = DateTime.Now;
                usersell.Sell_ColorName = d.EShopOrderDetails_ColorName;
                usersell.Sell_ID = 0;
                usersell.Sell_Price = d.EShopOrderDetails_Prices;
                usersell.Sell_PriceSum = d.EShopOrderDetails_PricesSum;
                usersell.Sell_Quantity = d.EShopOrderDetails_Quantity;
                usersell.Sell_SizeName = d.EShopOrderDetails_SizeName;
                usersell.UserCode = order.EShopOrder_UserCode;

                rtnList.Add(usersell);
            }
            return rtnList;
        }