Model not updating in MVC 2 application

I have a timesheet application that has a View where the user can select customers and tasks and add them to a dynamic table. This table is filled with the tasks and input fields for filling in hours worked.

For adding the new tasks in the dynamic table I use jQuery, so the savenewtask button is not a submit button. Instead I have a proper submit button for saving the hours when filled in.

The View is strongly typed to a model called TimesheetViewModel (see below). The controller passes the model to the View, and then the input fields are bound to properties in the model.

However, when I submit with the submit button and try to update the model in the Controller it doesn't update. It seemed from the Nerddinner tutorial (which I am using to learn MVC) that the model should automatically be updated using the values from the forms fields it had been bound to when you use UpdateModel(). But it doesn't. What am I doing wrong?

Here is all the relevant code:

View:

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
 <script src="../../Scripts/jquery-1.4.1.js" type="text/javascript"></script>
    <script src="../../Scripts/jquery-1.4.1.min.js" type="text/javascript"></script>
    <script type="text/javascript">
        $(document).ready(function () {
            //Hook onto the MakeID list's onchange event
            $("#CustomerId").change(function () {
                //build the request url
                var url = "Timesheet/CustomerTasks";
                //fire off the request, passing it the id which is the MakeID's selected item value
                $.getJSON(url, { id: $("#CustomerId").val() }, function (data) {
                    //Clear the Model list
                    $("#TaskId").empty();
                    //Foreach Model in the list, add a model option from the data returned
                    $.each(data, function (index, optionData) {
                        $("#TaskId").append("<option value='" + optionData.Id + "'>" + optionData.Name + "</option>");
                    });
                });
            }).change();
        });

    </script>
    <h2>Index</h2>

    <% using (Html.BeginForm())
       {%>
    <%: Html.ValidationSummary(true) %>
    <fieldset>
        <legend>Fields</legend>
        <div>
            <label for="Customers">
                Kund:</label>
            <%:Html.DropDownListFor(m => m.Customers, new SelectList(Model.Customers, "Id", "Name"), "Välj kund...", new { @id = "CustomerId" })%>
            &nbsp;&nbsp;
            <label for="Tasks">
                Aktiviteter:</label>
            <select id="TaskId">
            </select>
        </div>
        <p>
            <input type="button" value="Save new task" id="savenewtask" />            
        </p>

        <table width="100%">
        <%--<% foreach (var task in Model.Tasks)--%>
        <% foreach (var task in Model.WeekTasks)
           { %>
        <tr>
            <td>
                <%: task.Customer.Name %>
            </td>
            <td>
                <%: task.Name %>
            </td>
            <td>
                <% foreach (var ts in task.TimeSegment开发者_开发技巧s)
                   { %>
                <input class="hourInput" type="text" size="2" id="<%: ts.Task.CustomerId + '_' + ts.TaskId + '_' + ts.Date %>"
                    value="<%: ts.Hours %>" />
                <% } %>
            </td>
        </tr>
        <% } %>
    </table>
    <input type="submit" value="Save hours" id="savehours" />
    </fieldset>
    <% } %>

</asp:Content>

From the Controller:

private TimesheetViewModel _model;

public TimesheetController()
{
    _model = new TimesheetViewModel();
}

public ActionResult Index()
{

    return View(_model);
}

[HttpPost]
public ActionResult Index(FormCollection collection)
{
    try
    {
        UpdateModel(_model);
        _model.Save();
        return View(_model);
        //return RedirectToAction("Index");
    }
    catch
    {
        return View();
    }
}

The ViewModel:

public class TimesheetViewModel
{
    private TimesheetContainer _model; //TimesheeContainer is an Entity Framework model

    public TimesheetViewModel()
    {
        _model = new TimesheetContainer();
    }

    public IList<Customer> Customers
    { get { return _model.Customers.ToList(); } }

    public IList<Task> Tasks
    { get { return _model.Tasks.ToList(); } }

    public IList<Task> WeekTasks
    {
        get
        {
            //Get the time segments for the current week
            DateTime firstDayOfWeek = DateTime.Parse("2010-12-05");
            DateTime lastDayOfWeek = DateTime.Parse("2010-12-13");

            List<TimeSegment> timeSegments = new List<TimeSegment>();
            foreach (var timeSegment in _model.TimeSegments)
            {
                if(timeSegment.DateTimeDate > firstDayOfWeek && timeSegment.DateTimeDate < lastDayOfWeek)
                    timeSegments.Add(timeSegment);
            }
            //Group into tasks
            var tasks = from timeSegment in timeSegments
                       group timeSegment by timeSegment.Task
                        into t
                      select new { Task = t.Key };
            return tasks.Select(t => t.Task).ToList();
        }
    }

    public IList<TimeSegment> TimeSegments
    { get { return _model.TimeSegments.ToList(); } }

    public void Save()
    {
        _model.SaveChanges();
    }


    public void AddTimeSegments(Task task)
    {
        _model.AddToTasks(task);
        _model.SaveChanges();
    }

}

Partial class to get tasks for a specific week (only dummy week at this time for testing):

public partial class TimeSegment
{
    public DateTime DateTimeDate
    { get { return DateTime.Parse(Date); } }
}

Why is the model not updating, and what can I change to make it work?

Put a breakpoint on your first ActionResult Index(), is that getting called when you do the submit? you may need [HttpGet] on it, otherwise I think it gets both.