Asked  7 Months ago    Answers:  5   Viewed   37 times

Could any body explain, when to use

  1. TempData
  2. ViewBag
  3. ViewData

I have a requirement, where I need to set a value in a controller one, that controller will redirect to Controller Two and Controller Two will render the View.

I have tried to use ViewBag, the value gets lost by the time I reach Controller Two.

Can I know when to use and advantages or disadvantages?

Thanks

 Answers

45

1)TempData

Allows you to store data that will survive for a redirect. Internally it uses the Session as backing store, after the redirect is made the data is automatically evicted. The pattern is the following:

public ActionResult Foo()
{
    // store something into the tempdata that will be available during a single redirect
    TempData["foo"] = "bar";

    // you should always redirect if you store something into TempData to
    // a controller action that will consume this data
    return RedirectToAction("bar");
}

public ActionResult Bar()
{
    var foo = TempData["foo"];
    ...
}

2)ViewBag, ViewData

Allows you to store data in a controller action that will be used in the corresponding view. This assumes that the action returns a view and doesn't redirect. Lives only during the current request.

The pattern is the following:

public ActionResult Foo()
{
    ViewBag.Foo = "bar";
    return View();
}

and in the view:

@ViewBag.Foo

or with ViewData:

public ActionResult Foo()
{
    ViewData["Foo"] = "bar";
    return View();
}

and in the view:

@ViewData["Foo"]

ViewBag is just a dynamic wrapper around ViewData and exists only in ASP.NET MVC 3.

This being said, none of those two constructs should ever be used. You should use view models and strongly typed views. So the correct pattern is the following:

View model:

public class MyViewModel
{
    public string Foo { get; set; }
}

Action:

public Action Foo()
{
    var model = new MyViewModel { Foo = "bar" };
    return View(model);
}

Strongly typed view:

@model MyViewModel
@Model.Foo

After this brief introduction let's answer your question:

My requirement is I want to set a value in a controller one, that controller will redirect to ControllerTwo and Controller2 will render the View.

public class OneController: Controller
{
    public ActionResult Index()
    {
        TempData["foo"] = "bar";
        return RedirectToAction("index", "two");
    }
}

public class TwoController: Controller
{
    public ActionResult Index()
    {
        var model = new MyViewModel
        {
            Foo = TempData["foo"] as string
        };
        return View(model);
    }
}

and the corresponding view (~/Views/Two/Index.cshtml):

@model MyViewModel
@Html.DisplayFor(x => x.Foo)

There are drawbacks of using TempData as well: if the user hits F5 on the target page the data will be lost.

Personally I don't use TempData neither. It's because internally it uses Session and I disable session in my applications. I prefer a more RESTful way to achieve this. Which is: in the first controller action that performs the redirect store the object in your data store and user the generated unique id when redirecting. Then on the target action use this id to fetch back the initially stored object:

public class OneController: Controller
{
    public ActionResult Index()
    {
        var id = Repository.SaveData("foo");
        return RedirectToAction("index", "two", new { id = id });
    }
}

public class TwoController: Controller
{
    public ActionResult Index(string id)
    {
        var model = new MyViewModel
        {
            Foo = Repository.GetData(id)
        };
        return View(model);
    }
}

The view stays the same.

Tuesday, June 1, 2021
 
KouiK
answered 7 Months ago
74

$.validator.unobtrusive.parse("#frmAddItem"); will work. Do note that it must be in the partial that you load through ajax (below the form in the partial)

<form id="frmAddItem" method="POST" action="...">
    <!-- all the items -->
</form>
<script type="text/javascript">
    $.validator.unobtrusive.parse("#frmAddItem");
</script>
Friday, July 9, 2021
 
employeegts
answered 5 Months ago
95

The data you put in the ViewBag/ViewData is only available during the life-cycle of the request within which you populated it. MVC does not have post backs. If you need something to persist over more than a single request, you should use Session.

Here is a decent article about the differences between ViewData, ViewBag, and TempData: http://rachelappel.com/when-to-use-viewbag-viewdata-or-tempdata-in-asp.net-mvc-3-applications

Monday, August 2, 2021
 
freeMagee
answered 4 Months ago
10

Use TempData when you need data to be available for the next request, only.

TempData["myInfo"] = "my info";

Then in the next request, it will be there... but will be gone after that.

Use ViewBag for most of your extra-data needs to pass to your view, beyond the @model

ViewBag.MyInfo = "my info";

Then access it from your view.

Use ViewData to access/enter the exact same info as ViewBag, except as a collection instead of properties of a dynamic object.

ViewData["MyInfo"]

accesses exactly the same data as ViewBag.MyInfo

Note that I used strings, but these can store any object you wish.

Another thing to note: TempData and ViewData are both dictionaries that store object values, so you must cast those to their original type when you use them. ViewBag however uses dynamic, and you don't always need to cast that, since it is done at runtime. Some methods (like Extension methods) can not handle dynamic though, so you would need to cast in those cases.

Tuesday, August 3, 2021
 
rednammoc
answered 4 Months ago
54

I'm not sure if you mean Html helpers, or razor helpers when you say "helpers" In any case, I only create Html helpers when it's a small, idividual item like a control.

If you mean Razor helpers, then they are different from Partials in that you can call them like functions, passing whatever parameters you want. Partials are largely stuck with the "model" system (and of course Temp/ViewData/Bag.

It's all about how you want to work with the code.

As for your Partial. You have to include the suffix.

@Html.Partial("~/Views/ControllerName/_PartialView.cshtml", Model)
Wednesday, October 6, 2021
 
Vadim Rybak
answered 2 Months ago
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