Partial parameters using both ViewData Dictionary and the ViewBag deletes ViewBag data

Question

I need to pass some information to a partial cshtml view. I use a ViewDataDictionary and the ViewBag for that.

public ActionResult TaskPage(int ID = 0)
{
    ViewBag.breadcrumbs = new string[] {
        "List", "Tasks"
    };
    ViewBag.title = "Editing - My selected itemd";
    ViewBag.id = ID;
    return View();
}

and then when assembling the view I pass a ViewDataDictionary as well:

@Html.Partial("~/Views/Components/_Header.cshtml", new ViewDataDictionary { { "role", "task-page" } })

My _Header.cshmtl file uses both this dictionary and the ViewBag.

  ViewBag.breadcrumbs = ViewBag.breadcrumbs != null ? ViewBag.breadcrumbs : new string[] { };
  var role = ViewData["role"];

To my surprise, the ViewBag does not contain any data when I pass the ViewDataDictionary as well. How is that possible? Any idea how to better handle this?

What do you mean by "already in the ViewBag"? ViewBag is only kept for the life of one request. You can't put something in ViewBag, make a request, then expect it to be there in the next request. — Erik Funkenbusch, Mar 31 '15 at 14:38
The ViewBag is filled on the Controller. I added the specific code to clarify. — nest, Apr 01 '15 at 09:58
Looks like this one: http://stackoverflow.com/questions/5729784/cant-access-viewbag-in-a-partial-view-in-asp-net-mvc3 — Daniel Stackenland, Apr 01 '15 at 12:03
I have edited your title. Please see, "[Should questions include “tags” in their titles?](http://meta.stackexchange.com/questions/19190/)", where the consensus is "no, they should not". — John Saunders, Apr 01 '15 at 12:54
Ok. How can I let other viewers know they can find the solution in this post since nobody posted an actual answer? — nest, Apr 01 '15 at 12:56

score 2 · Accepted Answer · edited May 23 '17 at 11:43

See this post What's the difference between ViewData and ViewBag?

It would appear that "Internally ViewBag properties are stored as name/value pairs in the ViewData dictionary." which would suggest that you are overwriting the ViewBag when you pass a new ViewDataDictionary object

Taken from this blog post

public dynamic ViewBag 
{ 
    get 
    { 
         if (_dynamicViewData == null) 
        {
            _dynamicViewData = 
            new DynamicViewDataDictionary(() => ViewData); 
        }
        return _dynamicViewData;
    }
}

Partial parameters using both ViewData Dictionary and the ViewBag deletes ViewBag data

1 Answers1