ASP.NET MVC application doesn't like my for loops

Question

I rewrote a portion of my MVC application the other day and now I'm getting a RuntimeBinderException stating 'Cannot perform runtime binding on a null reference.'

I am assigning the ViewBag variable AvailableDocuments a collection (Dictionary) in the Controller and iterating through it in the View. I can make it through the first loop just fine, but when the code reaches the exit point of the second for loop it throws this exception. I have rewritten this a few different ways and always run into the same issue. The only way that I can get rid of this exception is to remove the second/third loops from this View. Also, I have used the debugger to verify that I am not receiving any null values in the collection and that the first loop isn't (for no reason) performing changes to this collection.

@foreach (KeyValuePair<int, string> doc in ViewBag.AvailableDocuments)
{
    <option value="@doc.Key" @((ViewBag.Product.Documents[0].OriginalDocID == doc.Key) ? "selected" : "")>@doc.Value</option>
}

This is the for loop that is repeated three times (to fill three dropdowns). The only thing that is changing is the index of Documents (which is not null).

Line 62: <select name="Doc1" style="width:300px;">
Line 63: <option value="-1">Don't Display a Document</option>
Line 64: @foreach (KeyValuePair<int, string> doc in ViewBag.AvailableDocuments)<--BREAK LINE
Line 65: {
Line 66: <option value="@doc.Key" @((ViewBag.Product.Documents[0].OriginalDocID == doc.Key) ? "selected" : "")>@doc.Value</option>'

And the message:

Exception Details: Microsoft.CSharp.RuntimeBinder.RuntimeBinderException: Cannot perform runtime binding on a null reference

Obvious candidates are ViewBag.Product and ViewBag.Product.Documents[0]. Double check them. — Henk Holterman
– Henk Holterman, Commented Jan 15, 2013 at 15:32
After removing the entire ternary expression the same exception is still thrown. I can actually empty out the loop and end up with the same error. — krik
– krik, Commented Jan 15, 2013 at 16:07

Jeff S · Accepted Answer · 2013-01-15 16:01:13Z

2

Are you reading the data in ViewBag.Product.Documents from a database or a webservice? If so, I'm guessing you are running into an issue with lazy loading (the data isn't being requested until it is needed). The exception is occurring because when the data is being requested, the source is no longer available.

In your code behind, add a ToList() on the assignment and see if that fixes the problem.:

ViewBag.Product.Documents = something.GetProductDocuments.ToList();

answered Jan 15, 2013 at 16:01

Jeff S

7,49432 silver badges32 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

krik Over a year ago

I was thinking it would be something to do with the source not being available any more but I couldn't hunt down the issue. Adding ToList did not work.

Jeff S Over a year ago

What does your code look like that is populating the ViewBag Product and Product.Documents properties?

Bob The Janitor · Accepted Answer · 2013-01-15 21:48:54Z

1

What happens if you create a collection of pocos with the desired data, could be as simple as this

public class OptionItem
{
   public int Id {get; set;}
   public string Text {get; set;}
}

and add it to a collection on the view model and pass that to the view? This way you know that all of the data is their before your going to your view. I would personally avoid using viewbag for something like this.

edited Jan 15, 2013 at 21:48

answered Jan 15, 2013 at 16:12

Bob The Janitor

20.8k10 gold badges51 silver badges72 bronze badges

1 Comment

krik Over a year ago

When passing the collection through a ViewModel I get the same issue.

Collectives™ on Stack Overflow

ASP.NET MVC application doesn't like my for loops

2 Answers 2

2 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related