Can ViewBag be null in MVC4?

Question

In MVC4, is it possible for ViewBag to ever be null? If so, under what scenarios could it be? If not, how do you know?

Specifically, I want to know if it can be null in a view. However, additional information about whether it can be null in a controller would be useful.

For example, do I need to perform a null check?

if (ViewBag != null && ViewBag.Something != null && ViewBag.Something.Foo == "Bar")
{
    // can ViewBag be null?
}

Answer 1

No, it can't.

The ViewBag property getter in WebViewPage looks like this:

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

Answer 2

ViewBag itself can't be null, so the first check

if (ViewBag != null) 

is useless