Question

I have a get and post method for my view, and in the get method I set the value of several ViewData objects. But when I call the post method these ViewData objects become null. Do I need to reset them in my post method? Here is my code :

public ActionResult Index()
    {
        ViewData["afceaststandings"] = GetStandingsForGrid("2017", "AFC East");
        ViewData["afccentralstandings"] = GetStandingsForGrid("2017", "AFC Central");
        ViewData["afcweststandings"] = GetStandingsForGrid("2017", "AFC West");

        return View("Index");
    }

[HttpPost]
    public ActionResult Index(QBRating qbm)
    {
        if (ModelState.IsValid)
        {
            string Result;
            double dblResult; 

            qbm.Completion = ((qbm.Completion - 30) * 0.05);

            if (qbm.Completion < 0)
            {
                qbm.Completion = 0;
            }

            if (qbm.Completion > 2.375)
            {
                qbm.Completion = 2.375;
            }

            qbm.Gain = ((qbm.Gain - 3) * 0.25);

            if (qbm.Gain < 0)
            {
                qbm.Gain = 0;
            }

            if (qbm.Gain > 2.375)
            {
                qbm.Gain = 2.375;
            }

            qbm.Touchdown = (qbm.Touchdown * 0.2);

            if (qbm.Touchdown > 2.375)
            {
                qbm.Touchdown = 2.375;
            }

            qbm.Interception = (2.375 - (qbm.Interception * 0.25));

            if (qbm.Interception < 0)
            {
                qbm.Interception = 0;
            }

            dblResult = Math.Round((((qbm.Completion + qbm.Gain + qbm.Touchdown + qbm.Interception) / 6) * 100), 2);

            Result = "QB Rating = " + Convert.ToString(dblResult);

            TempData["QBRating"] = Result;
        }

        //invalid - redisplay form with errors
        return View(qbm);
    }

Answer 1

Yes, values will need to be re-assigned to ViewData in your POST controller action as ViewData is not persisted across requests.

You could use TempData to persist data for a request (it is persisted in ViewData until next accessed); The default ITempDataProvider (SessionStateTempDataProvider) uses SessionState so, depending on what kind of Session Store you are using, the items you are putting into TempData may need to be serializable.