在 asp.net mvc5 中的多供应商电子商务商店中，根据商店订单限制计算购物车中的商店折扣

Question

我有一个多供应商电子商务商店，每个商店经理都可以管理他们对商店订单和商品的折扣。购物车模型如下：

    namespace myapp.Models
     public class Cart
     {
        [Key]
        public int RecordId { get; set; }
        public string CartId { get; set; }
        public Guid ItemId { get; set; }
        public Guid StoreId { get; set; }

        public Decimal? ShopDiscount { get; set; }
        public long ShopId { get; set; }
        [Display(Name = "Discount Time")]
        public string Duration { get; set; }
        [StringLength(100, ErrorMessage = "Must be less than 100 characters")]
        public string StoreName { get; set; }
        public decimal? Giftback { get; set; }
        [Display(Name = "Min order For Disc")]
        public Decimal? OrderLimit { get; set; }
        public int Count { get; set; }
        public decimal? Discount { get; set; }
        public System.DateTime DateCreated { get; set; }
        public virtual Item Item { get; set; }
      }
    }

我使用了实体框架和代码优先脚手架。 此外，在我的购物车模型类中，我使用了 shopdeal() 方法来计算商店级别的折扣，但它总是返回 0 并且确实如此。我觉得这个方法有问题。

    // shopdeal method to calculate shopdiscount for all items in cart 
     // 

            public decimal? ShopDeal()
        {
            decimal? shopdeal = 0;
           //get record with different shops so that calculate shop total 
     //separatly
            var results = db.Carts.Select(m => new { m.CartId, m.StoreId, 
    m.OrderLimit, m.ShopDiscount, m.Duration }).Distinct().ToList();

              // calculate total price of all items for a particular shop  
            foreach (var item in results)
            {
                decimal? shoptotal = (from cartItems in db.Carts
                                      where cartItems.CartId == ShoppingCartId
                                      && cartItems.Item.StoreId == 
    item.StoreId
                                      select 
    (decimal?)cartItems.Item.Price).Sum();
                if (shoptotal >= item.OrderLimit && item.Duration == 
    "Started")
                {
                    shopdeal = shopdeal + shoptotal * item.ShopDiscount / 100;
                }

            }

            return shopdeal;
        }

在上述方法中，我们尝试计算特定商店的所有商品的总价格，而不是将 shoptotal 与该商店的 shopdiscount (orderlimit) 进行比较，并检查其时间段（开始与否），如果这两个条件都为真，则适用 shopdiscount那家商店。如果用户从多个商店购买而不是适用于所有商店（使用 foreach 循环）。 如果有解决方法来获取每个商店的总价格并应用 shopdiscount 并获取总 shopdeal（total shopdiscount），请提供帮助。总功能如下：

        {
            // 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.CartId == ShoppingCartId
                              select (int?)cartItems.Count *
                              cartItems.Item.Price * (100 - 
                              cartItems.Item.Discount) / 100).Sum();
             // update total if shopdiscount available
            // why we need to apply shopdeal again? how to save result of 
             //shopdeal()
            total = total - ShopDeal(); 
            return total ?? decimal.Zero;
        }

 the above code works and no error is shown but the shopdiscount is always zero.any workaround to calculate and apply shopdiscount and reduce database queries.

Answer 1

谢谢大家，经过大量的努力，我按预期工作，在https://smartbook.pk/Items/DiscountItems中实现

     public decimal? ShopDeal()
        {
            decimal? shopdeal = 0;

            var results = (from cartItems in db.Carts
                           where cartItems.CartId == ShoppingCartId
                           select new { cartItems.StoreId,cartItems.OrderLimit,cartItems.Duration,cartItems.ShopDiscount }).Distinct().ToList();
                //db.Carts.Select(m => new { m.StoreId, m.OrderLimit, m.ShopDiscount, m.Giftback, m.Duration }.where()).Distinct().ToList();


            foreach (var item in results)
            {
                decimal? shoptotal = (from cartItems in db.Carts
                                      where cartItems.CartId == ShoppingCartId
                                      && cartItems.Item.StoreId == item.StoreId
                                      select (decimal?)cartItems.Item.Price).Sum();
                if (shoptotal >= item.OrderLimit && item.Duration == "Started")
                {
                    shopdeal = shopdeal + shoptotal * item.ShopDiscount / 100;
                }

            }

            return shopdeal;
        }

regards 
fiaz ahmed ranjha