Keep data stored in Session alive

Question

I have troubles managing data fetched by users on my app.

So far, if my understanding of ASP.NET MVC is what I think it is, I cannot put fetched data in static fields. For example, it would be a bad idea to do this:

private static List<MyObjects> listObjects = new List<MyObjects> { get; set;}

public List<MyObjects> GetMyObjects (int _objectID)
{
    using(MyDatabase database = new MyDatabase())
    {
        listObjects = (from o in database.MyObjects
                                where o.MatchingID == _objectID
                                select o).ToList();

        return listObjects;
    }
}

Because that would make the list of data available to all users on the web site. So I've read a few things and I thought that I needed to put things into MVC Session dictionary so that each user would browse through their own lists.

So I have these methods:

public List<MyObjects> GetMyObjects (int _objectID)
{
    using(MyDatabase database = new MyDatabase())
    {
        List<MyObjects> listObjects = (from o in database.MyObjects
                                where o.MatchingID == _objectID
                                select o).ToList();

        return listObjects;
    }
}

[HttpGet]
public ActionResult SeeItemsByID(int? _objectID)
{
    // Pre-validations to make sure that the ID is valid, then:
    List<MyObjects> listObjects = GetMyObjects((int)_objectID);

    Session["myObjects"] = listObjects;

    return RedirectToAction("SeeItems");
}

[HttpGet]
public ActionResult SeeItems()
{
    List<MyObjects> listObjects = Session["myObjects"] as List<MyObjects>;

    if(listObjects == null)
    {
        return RedirectToAction("Home");
    }

    return View(listObjects);
}


[HttpGet]
public ActionResult SeeItemsCompact()
{
    List<MyObjects> listObjects = Session["myObjects"] as List<MyObjects>;

    if(listObjects == null)
    {
        return RedirectToAction("Home");
    }

    return View(listObjects);
}

So let's resume the process:

First the user clicks on a link which calls the SeeItemsByID action, then it is redirected to the SeeItems action. In this view the user may click on a link to see the result "compacted" for any reasons. However, in my app, when the SeeItemsCompact method is called right after, all the Session data is lost.

How? And how could I keep this data alive?

It is recommanded to use `TempData` instead of `Session` in ASP.NET+MVC. — Bellash, May 05 '14 at 21:37
TempData uses a Session object internally, this just get destroyed after reading the value — pedrommuller, May 05 '14 at 22:35

score 0 · Answer 1 · answered May 06 '14 at 00:34

0

Is ID specific to the user? Is the list so big that this even makes sense? (it rarely does and if it does, you'll want to implement paging at the server to reduce the time of retrieval)

If it were me, I'd serialize the data to a file based on ID then when the user comes back and the session has expired, you don't need to re-retrieve the data. You can check the timestamp on the file and reload the data if the timestamp is too old.

answered May 06 '14 at 00:34

Dave Bush

2,382
15
12

Dave, paging is already implemented and that's not a problem. But I'm curious about serialize as you suggest it and I'd love to see an example, that would help me a lot. – hsim May 06 '14 at 16:25
1

http://stackoverflow.com/questions/16921652/how-to-write-a-json-file-in-c Of course in your case you'll want to use Server.MapPath() to put the file somewhere under your application's directory – Dave Bush May 06 '14 at 22:58

Keep data stored in Session alive

1 Answers1