Keep data between sessions

Question

I have an ASP.Netet MVC project where I file a report that requires quite resource of the machine in question of processing.

I have a Action that generates and another that returns the report data in an Object List, so I thought that by creating a static variable, I could save the report data and return it when needed.

private static List<MeuObjeto> DadosRelatorio = new List<MeuObjeto>();
public ActionResult MinhaAction ()
{
    // Limpando dados que já estavam.
    if (DadosRelatorio.Count() > 0)
    {
        DadosRelatorio.Clear();
    }

    ...
    // Preenchendo DadosRelatorio
    ...
}
public ActionResult OutraAction ()
{
  return Json(DadosRelatorio, JsonRequestBehavior.AllowGet);
}

The problem is that when 2 or more users simultaneously generate a report, the data of one overwrites the data of another.

I thought that by creating a static variable itself framework would manage a variable for each one on the server, but that’s not what happens, the same variable is for all users.

Is there any alternative?

Answer 1

In fact the static variable cannot be used. You need to create a session-based cache system or at least keep the information within the same session.

public ActionResult MinhaAction() {
    Session["relatorioX"] = MontaRelatorio();
    ...
}
public ActionResult OutraAction() => Json(Session["relatorioX"], JsonRequestBehavior.AllowGet);

I put in the Github for future reference.

The MontaRelatorio() probably returns a List<MeuObjeto>.

This is obviously a simplification, errors can occur if used like this but does what you were doing keeping the data per session instead of keeping it per application instance.

I believe in this case you can use TempData instead of Session hassle-free.

I do not know if this meets all needs but solves the problem according to what was specified in the question.

I would avoid putting a large amount of data between sessions but it’s a simple solution.

That one response in the OS has a cached solution. Other using the cache system itself framework.

ASP.NET Core has one new cache system more flexible (example of use).

Answer 2

A suggestion: use different names for reports, based on user identifiers (if applicable), where you can, through a BATCH running 1x a day, delete older reports based on their dates (if applicable).

This way Voce will have "user-dependent" reports (increasing disk use obviously), without relying exclusively on perennial variables.