Cannot apply indexing with [] to an expression of type 'System.Dynamic.DynamicObject'

Question

When I try to assign a value to the ViewBag I get the following error:

Cannot apply indexing with [] to an expression of type 'System.Dynamic.DynamicObject'

My code is as follows:

public ActionResult Success()
{
   ViewBag["SuccessBody"] = TempData["successBody"];
   return View();
}

PS: Why I do this you may ask? Because I am redirecting to the Success action and I needed something that persists across redirects. Then, I am assigning the value to ViewBag in order to pass the Value to a 'shared' view.

Aboard

But you can just use TempData. It will survive for one redirect. – Wagonage

Yes, but unfortunately shared views do not support the TempData objects. – Aboard

What version of Visual Studio are you using to compile this code? – Allyson

I am using Visual Studio 2012, upd4. – Aboard

Answer 1

Have you tried

ViewBag.SuccessBody = TempData["successBody"];

Alicealicea

What's the reason you can't use an indexer? – Lebanon

DynamicObjects do not expose their children as an array directly. This is just how it was designed. msdn.microsoft.com/en-us/library/… – Alicealicea

Ah I see, it's easy to miss. So a ViewBag can access them as dynamic properties, while ViewData can access them with an indexer? – Lebanon

Yes, Viewdata is a ViewDataDictionary which implements the interface IDictionary. That is why you can use an indexer on it. – Alicealicea

Answer 2

ViewBag is a dynamic wrapper for ViewData, so these two statements are the same:

ViewBag.SuccessBody = TempData["successBody"];
ViewData["SuccessBody"] = TempData["successBody"];

Cornhusk

Answer 3

ViewBag and ViewData seem kind of interchangable, but there are different rules as to how you access the data inside of them. Your issue pops up when you try to index into a ViewBag, which doesn't work.

For ViewBag, you dereference the items with a dot, like this.

ViewBag.MyItem

However, with ViewData, you access the items by indexing the appropriate key from the key value dictionary like this.

ViewData["MyItem"]

Linearity