Proper use of TempData in ASP.NET MVC3?

Question

I have an ASP.NET MVC3 application where my action generates a list of ids that I want to make available to a subsequent AJAX request. This is so that I can run a long process in the background and poll on it. The list of ids are the necessary input to this long running process. I don't want to pass them in the URL as a parameter, because the list could potentially be very long and cause issues in IE.

My Controller

public ActionResult Run()
{
    List<MyObjs> objs = _db.MyObjs.ToList<MyObjs>();

    string uniqueId = Guid.NewGuid().ToString();
    ViewData["UniqueID"] = uniqueId;
    TempData["ObjIdList" + uniqueId] = String.Join(",", objs .Select(o => o.ObjID).ToArray<int>());

    return View(objs);
}            

public void StartProcess(string uid)
{
    string ids = TempData["ObjIdList" + id].ToString().Split(',');
    ...        
}

My View

var uniqueId = '@ViewData["UniqueID"]';

$(document).ready(function (event) {
    $('#startProcess').click(function () {
        $.post("/Scheduler/StartProcess", { uid: uniqueId }, function () {
            getStatus();
        });
        event.preventDefault;
    });
});

function getStatus() {
    var r = new Date().getTime(); // cache killer for IE
    var url = '/Scheduler/GetCurrentProgress/' + uniqueId + "?r=" + r;
    $.get(url, function (data) {
        if (data != "100") {
            $('#status').html(data);
            setTimeout(function () { getStatus(); }, 100);
        } else {
            $('#status').html("Done");
        };
    });
}

This is working in my intial test, albeit on my laptop with one concurrent user. Is this safe, or is there a better way to pass this data?

score 11 · Accepted Answer · edited May 23 '17 at 12:00

11

Brandon

TempData is like ViewData, except that it persists for two successive requests making it useful for things like passing data between two different controller actions

Jason C

TempData in MVC actually persists until retrieved. As an FYI Tempdata is actually stored in a users SessionState so it is more like SessionData than ViewData

Taken from one of my questions responses - MVC3 Controller Action Result 'Remember' Passed-in Id

Essentially TempData is like a Session Property - (stored in the SessionState) used for communication between two successive requests to the controller. As if this is a good or bad practice well in your case I think it would be perfectly fine to pass data to the tempdata but their are other options, hidden fields among them. Another good link to look at is ASP.NET MVC - TempData - Good or bad practice

edited May 23 '17 at 12:00

Community

1
1

answered Oct 04 '12 at 23:20

Nate-Wilkins

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I think "TempData in MVC actually persists until retrieved" means that this is a safe pattern since the TempData has the GUID in the key. Do you agree? – Paul Oct 04 '12 at 23:22
Hmmm, no I don't think it does... Someone correct me if I'm wrong though this link "Persistence of TempData" might help http://stackoverflow.com/questions/3982465/tempdata-persisting-after-read-in-asp-net-mvc-2 I believe its fine since it does keep track of them separately but you always have to be careful with the state its in. – Nate-Wilkins Oct 04 '12 at 23:25

score 3 · Answer 2 · answered Oct 04 '12 at 23:27

The lifetime of TempData is very short.From the current request to the subsequent request. TempData is is using Session to store the data, behind the scenes. But the life time is shorter than the regular session variable, that is up to the subsequent request.

If you are sure you are going to make the ajax call right after the previous call where you set the TempData, you may use that. If you want more control, you may keep it in Session variable and destroy the session variable after you use it wherever you wanted n times.

I like the idea of using the `Session` instead. Like you said, more control. — Paul, Oct 04 '12 at 23:29

score 0 · Answer 3 · answered Oct 05 '12 at 05:27

0

Use TempData only when you want to pass values between Controllers in ASP .NET MVC.

answered Oct 05 '12 at 05:27

G . R

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Proper use of TempData in ASP.NET MVC3?

3 Answers3

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