How to persist the data in memory in MVC controller?

Question

Please look at the below action. When the user navigate the first time, creates a object, then while he navigates in the page, access again to the Action but through Ajax request and the data disappers (worksheets = null).

    private static List<Worksheet> worksheets;
    public ActionResult DoTest()
    {
        if (Request.IsAjaxRequest())
        {
            return PartialView("_Problems", worksheets[1]);
        }

        // first time
        worksheets = new List<Worksheet>()
        {
            new Worksheet("Hoja 1", ...),
            new Worksheet("Hoja 2", ...)
        };
        return View(worksheets[0]);
    }

My first solution was set the variable worksheets to static, but I supposed this is not a good practice. Am I doing a good way or are there another tweeks?

Answer 1

Stay away from static variables, especially if the data is user-dependent. You could take advantage of the ASP.NET Session object.

This can be easily done in your case by changing your worksheets field to a property that stores its value in the Session object. This way, it will be available on subsequent calls. Example:

  private List<Worksheet> worksheets
  {
    get{ return Session["worksheets"] as List<Worksheet>;}
    set{ Session["worksheets"] = value; }
  }

  public ActionResult DoTest()
  {
      if (Request.IsAjaxRequest())
      {
        return PartialView("_Problems", worksheets[1]);
      }

      // first time
      worksheets = new List<Worksheet>()
      {
          new Worksheet("Hoja 1", ...),
          new Worksheet("Hoja 2", ...)
      };
      return View(worksheets[0]);
  }