多个用户在购物车中看到相同的商品

Question

I have created a shopping cart using session to store the item being added to cart.Upon deployment i found out that the shopping cart is not unique to the user that is other user are getting items added to the cart by other user.

I tried to use the login username in the session name to make the session unique to that user but it is not working.

 public class ListOfDataset
 {

        static ListOfDataset()
        {

            string username = ClaimsPrincipal.Current.Identity.Name;

            // If the cart is not in the session, create one and put it there
            // Otherwise, get it from the session
            if (HttpContext.Current.Session[string.Format("ASPNETShoppingCart-{0}", username)] == null)
            {
                Instance = new ListOfDataset();
                Instance.Items = new List<DataSet>();
                HttpContext.Current.Session[string.Format("ASPNETShoppingCart-{0}", username)] = Instance;
            }
            else
            {
                Instance = (ListOfDataset)HttpContext.Current.Session[string.Format("ASPNETShoppingCart-{0}", username)];
            }
        }
}

Updated code,error in else statement-object reference not set and function ChekIfdatasetexist always return false:

 public class ListOfDataset
    {



        public static ListOfDataset Instance
        {
            get
            {

                ListOfDataset cart = null;

                if (HttpContext.Current.Session["ASPNETShoppingCart"] == null)
                {
                    cart = new ListOfDataset();

                    cart.Items = new List<DataSet>();

                    HttpContext.Current.Session["ASPNETShoppingCart"] = cart.Items;

                }
                else
                {

                    cart.Items =(List<DataSet> )HttpContext.Current.Session["ASPNETShoppingCart"];
                }

                return cart;
            }
        }

        public List<DataSet> Items { get; private set; }

        public void AddItem(DataSet itemdataset)
        {

            Items.Add(itemdataset);

            HttpContext.Current.Session["ASPNETShoppingCart"] = Items;
        }

        public bool CheckIfDataSetExist(string servicename)
        {
            DataSet DataSetexist = null;

            if (Items != null)
            {
                DataSetexist = Items.Where(i => i.DataSetName == servicename).FirstOrDefault();
            }


            if (DataSetexist != null) return true;

            return false;
        }
    }

Answer 1

There are two issues here.

1. As someone said in comments you have made the Instance member static, which means it will remain the same application wide and shared among users.
2. Session is not the best place to store per user data cause it will blow up your server memory and wont scale. Better use a database to store the data.