ASP.NET mvc : HOWTO: Update database after editing multiselectlist (listbox)

I'm really stuck at this: I have two listboxes populated from a database. I want to copy items from one list to the other. Then the changes must be saved in the database.

This is what I've got:

Custom ViewModel:

public class StudentModel
    {
        public IEnumerable<SelectListItem> NormalStudentsList { get; set; }
        public IEnumerable<SelectListItem> StudentsNoClassList { get; set; }
        public string[] NormalSelected { get; set; }
        public string[] NoClassSelected { get; set; }
        public string Save { get; set; }
    }

Controller:

public ActionResult IndexStudents(Docent docent, int id, int klasgroepid)
        {
            var studentModel = new StudentModel
            {
               NormalStudentsList = docent.GeefStudentenNormaalList(id, klasgroepid),
               StudentsNoClassList = docent.GeefStudentenNoClassList(id, klasgroepid)
            };

            return View(studentModel);
        }

        [HttpPost, Authorize]
        public ActionResult IndexStudentsResult(StudentModel model, string add, string remove)
        {
            ModelState.Clear();
           (if! string.IsNullOrEmpty(add))
               //update database
            SaveState(model);
            return View(model);
        }

But how can I update the database?? Using UpdateModel()? or should I work with FormCollection? But I need a formCollection to work with UpdateModel()... The Students table has a field named "ClassID", and when copying the rows from 1 list to the other, the ID has to change from the current ClassID to "0".

How can I do that? I'm really stuck at this... hope you can help.

This is my View

<%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master"  Inherits="System.Web.Mvc.ViewPage<ProjectenII.Models.Domain.StudentModel>"%>

<asp:Content ID="Content1" ContentPlace开发者_JS百科HolderID="TitleContent" runat="server">
    IndexStudents
</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
    <h2>IndexStudents</h2>

  <%using (Html.BeginForm()) { %>
    <%=Html.ListBoxFor(model => model.NormalSelected, new MultiSelectList(Model.NormalStudentsList, "StudentNummer", "Naam", Model.NormalSelected), new { size = "6" }); %>

    <input type="submit" name="add" 
                          id="add" value=">>" /><br />
    <%=Html.ListBoxFor(model => model.NoClassSelected, new MultiSelectList(Model.StudentsNoClassList, "StudentNummer", "Naam", Model.NoClassSelected)); %>
  <% } %>

  <%=Html.HiddenFor(model => model.Save) %>
  <input type="submit" name="apply" id="apply" value="Save!" />
</asp:Content>

Your problem is related to returning a List from the view... check this post by Phil Haack:

Model Binding To A List

Here you can see I ran into a similar problem. In my case a used checkboxes to select items in a list. The solution proposed guided me in the right direction but it wasn't the one I used, I used Phil's post.

My Post

Hope this helps.

We may also achieve using Editor helper, but making all of the multiselectlist elements selected before submit will work:

$("#NormalSelected option").prop("selected", true);

This will pass multiselectlist items to controller.