Refreshing ViewData in a method which returns Json

Question

I have a controller with a method which returns a partial view and generates ViewData. Then, I have some methods, each of them returns Json objects and ViewData. But, the ViewData is not getting refreshed. How to refresh it? Is this possible?

public ActionResult FirstMethod() {
    ViewData["someList"] = ...;
    return PartialView(someOtherList);
}

public JsonResult SomeMethod()
{
    ViewData["someNewList"] = ...;
    return new JsonResult { ... };
}

But, although SomeMethod() is called after FirstMethod(), the ViewData which I use in my view is someList.

ViewData will be cleared out in each request as explained by @Darin and you don't need to do that manually. Typically each action (unless it is a child action) corresponds to a browser request. So if you set some value to ViewData in one action it won't be available in other. — VJAI, May 29 '12 at 11:19

score 2 · Accepted Answer · answered May 29 '12 at 06:45

Is this possible?

No, it's not possible. The ViewData is a weakly typed dictionary which could be used (although I wouldn't recommend using it) to pass information between a controller and a view. Its lifetime is tied to that of the controller action execution pipeline. So once the view is rendered it's over. No controller, view, ViewData, ... exists anymore. Only HTML rendered in the client browser.

Then you send an AJAX request to the server again. This is completely new request that has nothing to do with the first one (which was used to render the view initially) and thus a new instance of the controller is created with its own ViewData. Setting ViewData in a controller action that returns JSON is useless because since this action will be invoked with javascript, all the information that you want to pass from the controller to the javascript success handler must be part of the JSON object that you return.

Why don't you recommend using ViewData? – petko_stankoski May 29 '12 at 06:48 — petko_stankoski, May 29 '12 at 06:48
Because it's weakly typed. I recommend using view models. – Darin Dimitrov May 29 '12 at 06:48 — Darin Dimitrov, May 29 '12 at 06:48

Refreshing ViewData in a method which returns Json

1 Answers1