ASP.NET MVC ViewBag list of anonymous class throws error on Count() method

Question

I have a serverside code where I'm returning a list of anonymous class from the database:

    public ActionResult DisplayMap()
    {
        ViewBag.Checkins = (from locationUpdate in db.LocationUpdates
                            select new
                            {
                                locationUpdate,
                                locationUpdate.User
                            }).ToList();
        return View();
    }

At the Razor page, I want to get the count of this list:

@if (ViewBag.Checkins.Count() > 0)
{ ... }

However, it throws an error:

An exception of type 'Microsoft.CSharp.RuntimeBinder.RuntimeBinderException' occurred 
in System.Core.dll but was not handled in user code.

Additional information: 'object' does not contain a definition for 'Count'

When I type ViewBag.Checkins in immediate window, I get:

ViewBag.Checkins
{System.Collections.Generic.List<<>f__AnonymousType6<MY_APP.LocationUpdate,MY_APP.User>>}
    [0]: { locationUpdate = {System.Data.Entity.DynamicProxies.LocationUpdate_4532566693B61EF657DDFF4186F1D6802EA1AC8D5267ED245EB95FEDC596E129}, User = {System.Data.Entity.DynamicProxies.User_816C8A417B45FE8609CD1F0076A5E6ECBAB0F309D83D2F8A7119044B1C6060CF} }

The Checkins object is indeed a List, and the data is correct. I've tried Count, Length too (without method call, just as properties) but no luck. What am I doing wrong?

Can you try @ViewBag.Checkins.ToString() and see what it outputs? — milagvoniduak, Apr 29 '14 at 13:25

D Stanley · Accepted Answer · 2019-11-07T20:47:07.353

38

ViewBag is dynamic, while Count is an extension method, which isn't supported dynamically (it has to be bound at compile time).

You can either cast to an IEnumerable<dynamic>:

@if (((IEnumerable<dynamic>)ViewBag.Checkins).Count() > 0)

or use the static method directly:

@if (Enumerable.Count(ViewBag.Checkins) > 0)

Or create a strongly-typed model with a Checkins property and avoid ViewBag altogether.

EDIT

Since you're just wanting to check if the count is greater than 0, Any is more appropriate (and may save some processing time depending on the scenario):

@if (Enumerable.Any(ViewBag.Checkins))

edited Nov 07 '19 at 20:47

answered Apr 29 '14 at 13:26

D Stanley

149,601
11
178
240

2

that is a solid answer. forgot about extension methods not supporting dynamic binding. `Enumerable.Count` worked, thanks. – Can Poyrazoğlu Apr 29 '14 at 13:39

score 1 · Answer 2 · edited Apr 29 '14 at 13:59

The viewbag is dynamic which make it an anonymous type generated as internal. It's better that you use view models instead.

and then call the view with its model, do something like this:

public class MyViewModel{
LocationUpdate LocationUpadte{get;set;}
User User{get;set;}
}

public ActionResult DisplayMap()
{
        var model = (from locationUpdate in db.LocationUpdates
                            select new MyViewModel
                            {
                                locationUpdate,
                                locationUpdate.User
                            }).ToList();
        return View(model);
}

then in you razor view

@Model.Count() will return the expected value

score 0 · Answer 3 · answered Apr 29 '14 at 13:27

0

You need to cast your object since the viewbag is dynamic. For example:

var list = ViewBag.List as List<int>();
list.Count();

answered Apr 29 '14 at 13:27

JuhaKangas

875
5
17

3

One wrinkle it that it's a list of an _anonymous type_. – D Stanley Apr 29 '14 at 13:28
you don't need to cast it. – milagvoniduak Apr 29 '14 at 13:29
I've tried casting to `List – Can Poyrazoğlu Apr 29 '14 at 13:30
@CanPoyrazoğlu Because it's _not_ a `List – D Stanley Apr 29 '14 at 13:36
but don't all types derive from `object`? – Can Poyrazoğlu Apr 29 '14 at 13:38
Yes but `List` is not covariant (otherwise you could add _any_ object to the list). See a related question [here](http://stackoverflow.com/questions/2033912/c-sharp-variance-problem-assigning-listderived-as-listbase). – D Stanley Apr 29 '14 at 13:45

score -3 · Answer 4 · edited Apr 25 '16 at 17:27

-3

You can do this:

- @if(ViewBag.Checkins.Count > 0)

edited Apr 25 '16 at 17:27

Vasfed

18,013
10
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answered Apr 25 '16 at 16:45

Alekz Varkatzas

11
2

ASP.NET MVC ViewBag list of anonymous class throws error on Count() method

4 Answers4