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?

Answer 1

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

Answer 2

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.

Answer 3

仅当您要在ASP .NET MVC中的控制器之间传递值时才使用TempData。