Can't access ViewBag in a partial view in ASP.NET MVC3

That should work without any problems. In my HomeController Index action I add a message to the ViewBag:

ViewBag.Message = "Welcome to ASP.NET MVC!";

On the Index View I add the partial view:

@Html.Partial("ViewName")

And on the partial view I render the message:

@ViewBag.Message

From the comments below: there seems to be a problem when you pass a model to the partial view. Then you can refer to the original ViewBag with

@ViewContext.Controller.ViewBag.Message

If you are using an overload of the Html.Partial() where viewData is one of the input parameters, for example:

@Html.Partial("PartialViewName", Model, new ViewDataDictionary(ViewBag))

then your partial view will not see data from your original ViewBag.

Remove new ViewDataDictionary(ViewBag), so you should write

@Html.Partial("PartialViewName", Model)

In a comment TehOne said:

I know this is a bit old, but for future reference, I solved this by using ViewContext.Controller.ViewBag.Property. Of course this means that the ViewBag property you are trying to access was set in the controller, but I think that is a common enough case.

Which is what worked for me.

Recently I was experiencing same problem, but the answers here were just workarounds as they propose not to use the overload of Html.Partial using viewData. But if you had to use these overloads I believe the correct answer is:

@Html.Partial(
     "PartialViewName",
     model_object,
     new ViewDataDictionary() { { "Value1InViewBag", ViewBag.Value1InViewBag }, { "Value2InViewBag", ViewBag.Value2InViewBag } }
)

I think this answer should be used if you need to pass different ViewDataDictionary (e.g. I us it for changing HtmlFieldPrefix) and because in the view you should know, what partial view wil need in ViewBag, so it should not be problem to name all the parameters from ViewBag to be copied into new ViewBag used in partial view (apparently ViewBag uses values from ViewData).

> In a general scenario, when you use Html.Partial;

Html.Partial("partialViewName");

The Model that is sent for parentView, can be used for in the partialViewName. Moreover, the ViewData which is send for parentView can also be used for partialViewName.

> As a special case, when you use Html.Partial and if you want to send Model..

Html.Partial("partialViewName", newModel);

You cannot reach the Model which was sent for parentView. Therefore, from now on the Model which is active in the partialViewName is the newModel. The viewData which is send for parentView can be used also for partialViewName.

> As a special case, when you use Html.Partial and if you want to send ViewDataDictionary..

The Model which is send for parentView can be used also for partialViewName

I.

@Html.Partial("partialViewName", new ViewDataDictionary { { "key", value }, { "key2", value2 }  })

Here, the ViewData which was sent for parentView overwrite by 'new ViewDataDictionary'.

Here, If there is a ViewBag which is for parentView, you cannot reach that if you write the code like above one.

II.

ViewDataDictionary viewDataDictionary =  new ViewDataDictionary();
viewDataDictionary.Add("key", value);
viewDataDictionary.Add("key2", value2);
@Html.Partial("partialViewName", viewDataDictionary)

This usage is same as first one (I.).

III.

ViewDataDictionary viewDataDictionary = ViewData; //If you use this code block,  ViewBag which is sent for parent View is not lost.
viewDataDictionary.Add("key", value);
viewDataDictionary.Add("key2", value2);
@Html.Partial("partialViewName", viewDataDictionary)

With this code block, You can reach the ViewData and ViewBag which are sent for parentView in the partialViewName