Storing custom objects in Sessions

What the general way of storing custom objects in sessions?

I’m planning on keeping my cart in a session throughout the web application. When that user logs out, the session will be cleared.

Class ShoppingCart
{
    private List<CartItem> Items = new List<CartItem>();

    public ShoppingCart()
    {
        this.Items = new List<CartItem>();
        if (HttpCurrent.Current["Cart"]!=null])
        {
            this.Items = ShoppingCart.loadCart(HttpCurrent.Current["User"]);
        }
    }
}

When the user signs in, I place the cart in a session, like:

Session["Cart"] = new ShoppingCart();

But do I have to write Session["Cart"] on each and every page? Isn’t there an easier way to do this? Also what about the Guest cart session? Where will I declare that?

I want each user session stored in a unique session, so that there’s no mixing up between the guest session and the member session.

Answers:

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Method 1

ASP.NET session corresponds to browser session – it is independent of whether user is authenticated (logged in) or not. So you should not have any issue with regards to guest/member sessions. I would advise you to expose the current shopping cart via static accessor property – for example

Class ShoppingCart {

    public static ShoppingCart Current
    {
      get 
      {
         var cart = HttpContext.Current.Session["Cart"] as ShoppingCart;
         if (null == cart)
         {
            cart = new ShoppingCart();
            HttpContext.Current.Session["Cart"] = cart;
         }
         return cart;
      }
    }

... // rest of the code

}

Few things to consider here:

1. Whenever web application or web server recycles/restarts, your in-process sessions would lost. It means you need persist your session in database at appropriate point.
2. You may use out of process session storage (database or different server) – you have to mark your shopping cart class as serializable in such case. There is performance cost to out-of-process sessions. As such, you are already storing session in database, so IMO, you should use in-proc sessions making sure to write dirty sessions into the database as soon as possible.

Method 2

Add it to a master page or you could add a static property to you ShoppingCart object

public static ShoppingCart GetCurrent
{
    get
    {
        if(HTTPContext.Current.Session["CurrentCart"] == null)
        {
            HTTPContext.Current.Session["CurrentCart"] = new ShoppingCart();
        }
        return HTTPContext.Current.Session["CurrentCart"] as ShoppingCart;
    }
}

Method 3

Generic Extension Method definition in a static class:

public static T GetSession<T>(string key) =>  HttpContext.Current?.Session?[key] != null ? (T)HttpContext.Current.Session[key] : default(T);

usage example
implicit

var myCart = GetSession<ShoppingCart>("myKey");

inference

ShoppingCart myCart2 = GetSession("myKey");

check if exists

if(myCart != default(ShoppingCart)){
    // do stuff
}

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0