ASP.Net MVC - List binding from View to Controller [duplicate]

Question

I'm having trouble binding a basic list of values to the model in my post action in the controller. The list is returning null.

I have a viewmodel which looks like this:

public class DistributionListFormModel : FormViewModel
{
    [Required(ErrorMessage = "The title is required")]
    public string Title { get; set; }

    public List<DistributionItem> DistributionItems { get; set; }
}

public class DistributionItem
{
    public string LabelText { get; set; }
    public bool Signup { get; set; }
}

Ok - so in my controller, I populate the DistributionItems list with some dud values within the index method. And here is a snapshot of my view:

<div class="o-wrapper">

@using (Html.BeginForm("Submit", "MyController", FormMethod.Post))
{
    foreach (var item in Model.DistributionItems)
     {
         <p>@item.LabelText</p>
         @Html.CheckBoxFor(m => item.Signup)

    }
    <button type="submit">SUBMIT</button>

}

Any idea why the DistributionItems list is null in the post controller? I found some articles but they all relate to very older versions of ASP.Net...

Thanks!!

Post the code where you're passing the model to the view and all about the model creation. — dcg
– dcg, Commented Jul 26, 2017 at 19:50

Eric Petroelje · Accepted Answer · 2017-07-26 20:07:46Z

1

This is one of those maddening things that exposes the limitations of model binding with lists in MVC.

What it comes down to is that you have to use a for loop with an indexer - a foreach loop won't work:

for (int i = 0; i < Model.DistributionItems.Count; i++)
{
     <p>@Model.DistributionsItems[i].LabelText</p>
     @Html.CheckBoxFor(m => m.DistributionsItems[i].Signup)
}

Here are a few references related to this that go into some more detail:

Model Binding to a List MVC 4

ASP.NET MVC 5 model binding list is empty

http://haacked.com/archive/2008/10/23/model-binding-to-a-list.aspx/

edited Jul 26, 2017 at 20:07

answered Jul 26, 2017 at 19:53

Eric Petroelje

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6 Comments

Eric Petroelje Over a year ago

Wow, two downvotes and no comments, did I miss something obviously wrong here?

John H Over a year ago

@Pat There is absolutely something wrong with using a foreach. The HTML helpers do not generate unique indices in the rendered HTML, which means the model binder is not able to determine how the elements should be associated when binding to a collection.

John H Over a year ago

@EricPetroelje No, your answer is correct. The reason I linked to the duplicate, though, is because people should understand how editor templates work, as they make this sort of situation so trivial to deal with.

Eric Petroelje Over a year ago

@JohnH - Yup, editor templates are the best way to handle this scenario. Just didn't want to introduce additional concepts that might cloud the core issue that the OP is having here. Added my close vote as well.

Pat Over a year ago

Ah okay I see what you're saying, its only an issue with implicit binding then. Good to know -- I stand corrected

|

Ricky Sett · Accepted Answer · 2017-07-26 20:05:38Z

0

Have you tried doing this:

foreach (var item in Model)
{
    @Html.HiddenFor(model => item.LabelText )
    @Html.LabelFor(model=> item.LabelText )
    @Html.CheckBoxFor(model => item.Signup)
}

I've had this issue before and what's happening is your controller doesn't see the object. All you're returning is a list of boolean.

answered Jul 26, 2017 at 20:05

Ricky Sett

597 bronze badges

1 Comment

Ricky Sett Over a year ago

If this doesn't work you can always build your list with jQuery and post it with Ajax.

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