public ActionResult AddToCart(int id)
        {

            // Retrieve the album from the database
            var addedAlbum = storeDB.Albums
                .Single(album => album.AlbumId == id);

            // Add it to the shopping cart
            var cart = ShoppingCart.GetCart(this.HttpContext);

            cart.AddToCart(addedAlbum);

            // Go back to the main store page for more shopping
            return RedirectToAction("Index");
        }

 public const string CartSessionKey = "CartId";
       
 public static ShoppingCart GetCart(HttpContextBase context)
        {
            var cart = new ShoppingCart();
            cart.ShoppingCartId = cart.GetCartId(context);
            return cart;
        }

        // 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();
        }