/MvcMusicStore/Models/ShoppingCart.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.Mvc;



namespace MvcMusicStore.Models

{

    public partial class ShoppingCart

    {

        MusicStoreEntities storeDB = new MusicStoreEntities();



        string ShoppingCartId { get; set; }



        public const string CartSessionKey = "CartId";



        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(Album album)

        {

            // Get the matching cart and album instances

            var cartItem = storeDB.Carts.SingleOrDefault(

c => c.CartId == ShoppingCartId

&& c.AlbumId == album.AlbumId);



            if (cartItem == null)

            {

                // Create a new cart item if no cart item exists

                cartItem = new Cart

                {

                    AlbumId = album.AlbumId,

                    CartId = ShoppingCartId,

                    Count = 1,

                    DateCreated = DateTime.Now

                };



                storeDB.Carts.Add(cartItem);

            }

            else

            {

                // If the item does exist in the cart, then add one to the quantity

                cartItem.Count++;

            }



            // Save changes

            storeDB.SaveChanges();

        }



        public int RemoveFromCart(int id)

        {

            // Get the cart

            var cartItem = storeDB.Carts.Single(

cart => cart.CartId == ShoppingCartId

&& cart.RecordId == id);



            int itemCount = 0;



            if (cartItem != null)

            {

                if (cartItem.Count > 1)

                {

                    cartItem.Count--;

                    itemCount = cartItem.Count;

                }

                else

                {

                    storeDB.Carts.Remove(cartItem);

                }



                // Save changes

                storeDB.SaveChanges();

            }



            return itemCount;

        }



        public void EmptyCart()

        {

            var cartItems = storeDB.Carts.Where(cart => cart.CartId == ShoppingCartId);



            foreach (var cartItem in cartItems)

            {

                storeDB.Carts.Remove(cartItem);

            }



            // Save changes

            storeDB.SaveChanges();

        }



        public List<Cart> GetCartItems()

        {

            return storeDB.Carts.Where(cart => cart.CartId == ShoppingCartId).ToList();

        }



        public int GetCount()

        {

            // Get the count of each item in the cart and sum them up

            int? count = (from cartItems in storeDB.Carts

                          where cartItems.CartId == 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 storeDB.Carts

                              where cartItems.CartId == ShoppingCartId

                              select (int?)cartItems.Count * cartItems.Album.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

                {

                    AlbumId = item.AlbumId,

                    OrderId = order.OrderId,

                    UnitPrice = item.Album.Price,

                    Quantity = item.Count

                };



                // Set the order total of the shopping cart

                orderTotal += (item.Count * item.Album.Price);



                storeDB.OrderDetails.Add(orderDetail);



            }



            // Set the order's total to the orderTotal count

            order.Total = orderTotal;



            // Save the order

            storeDB.SaveChanges();



            // Empty the shopping cart

            EmptyCart();



            // Return the OrderId as the confirmation number

            return order.OrderId;

        }



        // 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 = storeDB.Carts.Where(c => c.CartId == ShoppingCartId);



            foreach (Cart item in shoppingCart)

            {

                item.CartId = userName;

            }

            storeDB.SaveChanges();

        }

    }

}