MVC BeginCollectionItem

Question

I'm having some issue getting my partial view BeginCollectionItem to save to the database. I have a form which has a dynamic number of "sections" that can be added to the page, and within each of these fields there is a text box where the user can enter the section name.

As far as I can tell the BeginCollectionItem within the partial view is working properly, however I cannot post the info to the database. In my other forms I have used a [bind()] to send the data to the database, is it possible to get this into a list and then post that via a bind?

I've included my code below: The Model:

namespace project.Models.SetupViewModels
{
    public class SOPTopTemplateBuilderViewModel
    {
        public List<Section> Section { get; set; }
    }

    public class Section {
        public int SectionId { get; set; }
        public string SectionText { get; set; }
        public string TopTempId { get; set; }
    }
}

cshtml:

    @model IEnumerable<project.Models.SetupViewModels.Section>
    @using (Html.BeginForm("SOPTopTemplateBuilder", "Setup", FormMethod.Post))
    {
     <div class="main-holder" id="theform">
     @foreach(var item in Model)
     {
         @Html.Partial("_SectionCreator", item)
     }
     </div>
     <button id="add" type="button">Add</button>
         <div class="form-group submit-row">
              <div class="col-12 float-to-right">
                   <input type="submit" class="btn btn-default" value="continue" />
              </div>
         </div>
    }
@section Scripts {
    <script>
$(document).ready(function () {
        var url = '@Url.Action("AddSection")';
        var form = $('form');
        var recipients = $('#theform');
        $('#add').click(function() {
            $.post(url, function(response) {
                recipients.append(response);
                // Reparse the validator for client side validation
                form.data('validator', null);
                $.validator.unobtrusive.parse(form);
                });
            });
        });
    </script>
}

Partial View:

@model project.Models.SetupViewModels.Section
@using HtmlHelpers.BeginCollectionItemCore

@using (Html.BeginCollectionItem("Section"))
{
    <div class="new-section">
        <div>
            <p>New Section</p>
             @Html.HiddenFor(m => m.SectionId, new { @class="id" })
            @Html.EditorFor(m => m.SectionText, new { @class = "form-control limit-form"})
         </div>
    </div>
}

Controller:

[HttpPost]
public PartialViewResult AddSection()
{      
      return PartialView("_SectionCreator", new Section());
}

[HttpGet]
public ActionResult SOPTopTemplateBuilder(){

      List<Section> model = new List<Section>();

      return View(model);
}

[HttpPost]
public ActionResult SOPTopTemplateBuilder(IEnumerable<Section> soptop)
{
      if (ModelState.IsValid)
      {}
      return View(soptop);
}

Answer 1

Your use of Html.BeginCollectionItem("Section") perpends Section[xxxx] to the name attribute (where xxxx is a Guid) so that you generating inputs with

<input name="Section[xxxx].SectionId" .... />

which posts back to a model containing a collection property named Sections.

Since you already have a model with that property, you can change the POST method to

[HttpPost]
public ActionResult SOPTopTemplateBuilder(SOPTopTemplateBuilderViewModel soptop)

other options include

1. Using your existing POST method and omitting the "Section" prefix using Html.BeginCollectionItem("") which will generate name="[xxxx].SectionId"
2. Changing the POST method signature to public ActionResult SOPTopTemplateBuilder(IEnumerable<Section> section) (where the name of the parameter matches the name of the prefix)
3. Using a BindAttribute to 'strip' the prefix from the form values public ActionResult SOPTopTemplateBuilder([Bind(Prefix = "Section")]IEnumerable<Section> soptop)

As a side note, your editing data, so you should always use a view model (say public class SectionViewModel) rather than using data models in your view. - What is ViewModel in MVC?