Question

Can someone explain why the model object is null. I checked the post values coming across the wire and all of them are populated.

Using VS2010 Beta 2,WinXp SP2,however this works in VS2008 ??!!

Yellow screen of death message

Server Error in ‘/’ Application.
Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:

Line 17:             <p>
Line 18:                 <label for="id">id:</label>
Line 19:                 <%= Html.TextBox("id", Model.id) %> <--Error 
Line 20:                 <%= Html.ValidationMessage("id", "*") %>
Line 21:             </p>

Controller Code

 [AcceptVerbs(HttpVerbs.Post)]
    public ActionResult Edit(Contact contactToEdit)
    {
        if (contactToEdit.FirstName.Trim().Length == 0)
            ModelState.AddModelError("FirstName", "First name is required.");
        if (contactToEdit.Lastname.Trim().Length == 0)
            ModelState.AddModelError("LastName", "Last name is required.");
        if (contactToEdit.Phone.Length > 0 && !Regex.IsMatch(contactToEdit.Phone, @"((\(\d{3}\) ?)|(\d{3}-))?\d{3}-\d{4}"))
            ModelState.AddModelError("Phone", "Invalid phone number.");
        if (contactToEdit.Email.Length > 0 && !Regex.IsMatch(contactToEdit.Email, @"^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$"))
            ModelState.AddModelError("Email", "Invalid email address.");

        if (!ModelState.IsValid)
            return View();
        try
        {
            // TODO: Add update logic here
            var con = (from c in _entities.Contacts
                       where c.id == contactToEdit.id
                       select c).FirstOrDefault();
            _entities.ApplyCurrentValues(con.EntityKey.EntitySetName, contactToEdit);
            _entities.SaveChanges();


            return RedirectToAction("Index");
        }
        catch
        {
            return View();
        }
    }

Snippet of View code

<%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<JQGallery.Models.Contact>" %>
...
<%= Html.ValidationSummary("Edit was unsuccessful. Please correct the errors and try again.") %>

<% using (Html.BeginForm()) {%>

    <fieldset>
        <legend>Fields</legend>
        <p>
            <label for="id">id:</label>
            <%= Html.TextBox("id", Model.id) %>
            <%= Html.ValidationMessage("id", "*") %>
        </p>
        <p>
            <label for="FirstName">FirstName:</label>
            <%= Html.TextBox("FirstName", Model.FirstName) %>
            <%= Html.ValidationMessage("FirstName", "*") %>
        </p>
        <p>
        ...

Answer 1

The Model object is null because you’re not setting it. In your POST controller method, neither of the View results you return is setting a model (after the if (!ModelState.IsValid) line and in your catch block). In both those cases, you need to reload your model from somewhere so the view can redisplay its data.