Why is my MVC form failing to post a list of objects?

MVC Form: Object list submission failed

Problem Description

In an MVC application, a form containing a list of objects does not submit the list to the controller correctly. After submitting the form, the list of objects received by the controller is empty.

Solution

The problem stems from the missing index of the list item in the form element. The model binder requires indexes to distinguish elements in the list.

Implementation details

To solve this problem, use templates instead of partial views.

1. Create editor template

In the "EditorTemplates" folder under the view folder, create an editor template named "PlanCompareViewModel.cshtml". Place the following code into your template:

<code>@model PlanCompareViewModel
<div>
    @Html.HiddenFor(p => p.PlanID)
    @Html.HiddenFor(p => p.CurrentPlan)
    @Html.CheckBoxFor(p => p.ShouldCompare)
</div></code>

2. Modify the parent view

Update the parent view as follows:

<code>@model IEnumerable<plancompareviewmodel>
@using (Html.BeginForm("ComparePlans", "Plans", FormMethod.Post, new { id = "compareForm" }))
{
    <div>
        @Html.EditorForModel()
    </div>
}</code>

DisplayTemplates and EditorTemplates automatically handle indexing for collections, ensuring the model binder creates the correct list of objects.

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