TempData moving from view to controler

Question

I am attempting to call a controller via an actionLink() in a view. This controller get's data from a TempData repository. However, it seems that no matter what I do, if I set the TempData repository in the view, it won't go over to the controller? Should I use ViewData instead? What is your recommendation for a system such as that?

Thanks

Answer 1

TempData, nor ViewData is supposed to be set in a view. A view is supposed to consume data that has been stored in those structures inside your controller actions (well, actually it isn't, a view is supposed to consume a view model but that's another topic).

TempData could be used when you want to persist information between two redirects. It should be set inside a controller action which redirects to another controller action that will read the data:

public ActionResult Foo()
{
    SomeModel model = ...
    TempData["foo"] = model;
    return RedirectToAction("Bar");
}

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

So a controller action should get data from the TempData structure only if this action has been invoked after a redirect from another action that set the data. Such controller action should never be invoked from a view because if you have a view this means that this view was rendered from a controller action that presumably set the data into TempData but there is always a risk (if the view performs in between a request to the server - AJAX or something), the TempData will be lost.

For your case, when a view needs to invoke the server there are basically 3 techniques:

• Use an HTML <form> with input fields that will send the data to the server
• Use an anchor and pass data as query string parameters to the controller
• Use javascript and send an AJAX request or a redirect to the server

Answer 2

You should set the TempData value beforehand, in the controller that renders your view. The value will then get picked up by the controller action that renders your second (ActionLink) view.