商城系统简单购物车结构设计代码实现

  public class ShopCart
    {
        private string UserId;

        public List<CartItem> CartItems { get; set; } = new List<CartItem>();

        private ShopCart()
        {

        }
        public ShopCart(string userId)
        {
            this.UserId = userId;
            InitCart();
        }

        #region 初始化购物车
        private void InitCart()
        {
            CartItems = new ShopCarBll().GetListByUserId(UserId) ?? (List<CartItem>)new List<CartItem>();
        }
        #endregion

        #region 对购物车进行操作
        /// <summary>
        /// 添加商品
        /// </summary>
        /// <param name="productId"></param>
        /// <param name="count"></param>
        /// <returns></returns>
        public bool AddProduct(int productId, int count)
        {
            var productModel = new ProductBll().GetModel(productId);
            if (productModel != null)
            {
                if (CartItems.Any(x => x.ProductId == productId))
                {
                    return ModifyCount(productId, count);
                }
                else
                {
                    //更新购物车到数据库中做持外化
                    if (new ShopCarBll().Add(UserId, productId, count))
                    {
                        CartItems.Add(new CartItem(productModel.Id, productModel.Price, count));
                        return true;
                    }
                }
            }
            return false;
        }

        /// <summary>
        /// 修改商品数量
        /// </summary>
        /// <param name="productId"></param>
        /// <param name="count"></param>
        /// <returns></returns>
        public bool ModifyCount(int productId, int count)
        {
            var item = CartItems.FirstOrDefault(x => x.ProductId == productId);
            if (item != null)
            {
                if (new ShopCarBll().Mobify(UserId, productId, count))
                {
                    //更新到数据库中
                    item.Count = count;
                    return true;
                }
            }
            return false;
        }
        /// <summary>
        /// 移除商品
        /// </summary>
        /// <param name="productId"></param>
        /// <returns></returns>
        public bool RemoveProduct(int productId)
        {
            var item = CartItems.FirstOrDefault(x => x.ProductId == productId);
            if (item != null)
            {
                if (new ShopCarBll().Remove(UserId, productId))
                {
                    //更新到数据库中
                    CartItems.Remove(item);
                    return true;
                }
            }
            return false;
        }
        #endregion

        /// <summary>
        /// 获取购物车总价
        /// </summary>
        /// <returns></returns>
        public decimal GetSumFee()
        {
            return CartItems.Sum(x => x.Count * x.Count);
        }
    }

    public class CartItem
    {
        public int ProductId { get; set; }
        public int Count { get; set; }

        public decimal Price { get; set; }

        public CartItem(int productId, decimal price, int count)
        {
            this.ProductId = productId;
            this.Count = count;
            this.Price = price;
        }
    }
接着写测试类

 public class testCart
    {
        public void Test()
        {
            string userId = "123123123";
            ShopCart myCart = new ShopCart(userId);
            myCart.AddProduct(1001, 1);
            myCart.AddProduct(1002, 3);
            myCart.AddProduct(1003, 2);

            myCart.ModifyCount(1002, 5);//修改购物车数量
            myCart.RemoveProduct(1003);//删除购物车商品
            decimal sumFee = myCart.GetSumFee();//获取所有购物车金额
        }
    }

完工