MVC view returning null value

Question

I am making my MVC application. I am creating a form, with a table in it. A table is supposed to contain users and grades that they have (something like mark sheet at schools). I want the marks to be modifable, so I made them of type TextBox with default value as in database, but apparently, when I press "Apply changes" button, the controller sees the list of all marks as null. Why is it so?
My View (a part of it):

@Scripts.Render("~/bundles/jquery")
@Scripts.Render("~/bundles/bootstrap")
@model ClassDeclarationsThsesis.Models.ClassesViewViewModel


@{
    ViewBag.Title = "ClassesView";
}
<h2>ClassesView</h2>
<select id="sel">
    <option value="week">Current week</option>
    <option value="total">Total</option>
</select>
@{
    int i = 0;
    int inside = 0;
}
@using (Html.BeginForm("ClassesView", "Account", FormMethod.Post, new { @class = "form-horizontal", role = "form" }))
{
        <div id="week">
        <table border="1" width="500">
            <tr>
                <th>Surname</th>
                <th>Name</th>
                @foreach (var task in Model.current)
                {
                    <th>@task.name</th>
                }
                <th>Total</th>
            </tr>
            @{
                int counter = 0;
                int counter1 = 0;
            }
            @foreach (var user in Model.curr_users)
            {

                if (user.user_type.Replace(" ", String.Empty) == 1.ToString())
                {

                    <tr>
                        <th>@user.surname</th>
                        <th>@user.name</th>
                        @foreach (var task in Model.current)
                        {
                            foreach (var grade in Model.grading)
                            {
                                if (user.user_id == grade.user_id)
                                {
                                    if (task.task_id == grade.task_id)
                                    {
                                        inside = task.value;
                                        i = i + task.value;
                                        counter1++;
                                    }

                                }

                            }
                            <th>@Html.TextBoxFor(m => m.points[counter + counter1 - 1], new { @class = "form-control", @Value = @inside, style = "width:50px;" })</th>
                            inside = 0;
                        }
                        <th>
                            @i
                        </th>
                        @Html.HiddenFor(m => m.class_id)
                        @Html.HiddenFor(m => m.student_id)
                    </tr>
                }
                i = 0;
                counter++;
            }
        </table>
        <input type="submit" class="btn btn-default" value="Apply changes" />

    </div>
                }

points that I used here is List<int> in ClassesViewViewModel. What am I doing wrong?
EDIT:
Added the controller:

public ActionResult ClassesView(ClassesViewViewModel value)
{
    ClassDeclarationsDBEntities4 entities = new ClassDeclarationsDBEntities4();
    ClassesViewViewModel model = new ClassesViewViewModel();
    model.users = entities.Users.ToList();
    model.tasks = entities.Tasks.ToList();
    model.group_id = value.group_id;
    model.class_id = value.class_id;
    model.grading = entities.Gradings.ToList();
    model.s_u = entities.Subjects_Users.ToList();
    model.t = new List<ClassDeclarationsThsesis.Classes.Task>();
    model.current = new List<ClassDeclarationsThsesis.Classes.Task>();
    model.curr_users = new List<ClassDeclarationsThsesis.Classes.User>();
    DateTime max = DateTime.MinValue;
    foreach (var task in model.tasks)
    {
        if (task.class_id == model.class_id)
        {
            model.t.Add(new ClassDeclarationsThsesis.Classes.Task(task.task_id, task.class_id, task.name, task.points, task.deadline));
        }


    }
    foreach (var task in model.t)
    {
        if (DateTime.Compare(task.deadline, max) > 0)
        {
            max = task.deadline;
        }
    }
    foreach (var task in model.t)
    {
        if (DateTime.Compare(task.deadline, max) == 0)
        {
            model.current.Add(task);
        }
    }
    foreach (var s_u in model.s_u)
    {
        if (s_u.class_id == model.class_id && s_u.group_id == model.group_id)
        {
            foreach (var user in model.users)
            {
                if (user.user_id == s_u.user_id)
                {
                    model.curr_users.Add(new ClassDeclarationsThsesis.Classes.User(user.name, user.surname, user.user_id, user.user_type, user.email, user.password));
                }

            }
        }

    }

    if (ModelState.IsValid)
    {
        for(int i=0;i<model.points.Count();i++)
        {
            //getting null here
        }
    }
    else
    {
        return View(model);
    }


    return View(model);
}

It's hard to tell with this code, but probably because your indices are non sequential and/or do not start with zero. For the model binding to work, list indices must begin with zero and be sequential with no gaps. — GSerg, Jan 16 '17 at 07:04
Your controller does not make sense either. You first build the model manually (like you would from a `get` action to return the model to a view), then you call `ModelState.IsValid` (like you would from a `post` where you receive an already built model from outside), then you return view(model) like it's a `get` again, and in the entire process the only values you are using from the bound model are `group_id` and `class_id`. Make up your mind. — GSerg, Jan 16 '17 at 07:08
You cannot use a `for` loop to generate form controls for a collection - refer [this answer](http://stackoverflow.com/questions/30094047/html-table-to-ado-net-datatable/30094943#30094943). And never set the `value` attribute when using the `HtmlHelper` methods — , Jan 16 '17 at 07:09
@StephenMuecke `points` is a `list` and they are using `m => m.points[counter + counter1 - 1]` which does generate indices. — GSerg, Jan 16 '17 at 07:11
@GSerg Yes, but it will never get correct 2-way model binding (and as you have noted, the `if` blocks means that indexers are likely not zero-based and consecutive) — , Jan 16 '17 at 07:13
@StephenMuecke Yes, they most likely have messed up indices, but I always thought the approach was correct in principle (i.e. having an `IList` and using `EditorFor(m => m.list[index])`). It certainly has fixed the naive `foreach` loops and provided two-way binding. I am aware of editortemplate-based ways and [I like them](http://stackoverflow.com/q/25333332/11683), but can it be said this one is not correct? — GSerg, Jan 16 '17 at 07:21
@GSerg, There can be problems if OP would need to return the view (if say `ModelState` was invalid) because of the way the `HtmlHelper` metohds use values of `ModelState`. Using a custom `EditorTemplate` (in which case all that's needed is `EditorFor(m => m.List)`) or a `for` loop is always best — , Jan 16 '17 at 07:26

score 1 · Accepted Answer · answered Jan 16 '17 at 07:26

1) You should change the "value" as "model" at HttpPost action method.

public ActionResult ClassesView(ClassesViewViewModel model)

2) There are a lot of line at your action method.You should learn repository and service patterns.Briefly you should put the db reading,inserting,updating line in a repository class.You should make repository classes for each entities.Business logic ( validation etc ) must be in the service classes.

score -1 · Answer 2 · answered Jan 16 '17 at 07:31

-1

Okay so I found the answer. I changed value in controller to model and also corrected the counter in view to ensure that the values are consecutive, starting from 0. Thank you for your support.

answered Jan 16 '17 at 07:31

Maciej Miśkiewicz

301
1
4
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1

Then why have you accepted an answer that has nothing to do with you issue - changing the parameter name has nothing to do with it (unless you model has a property name `value` which it does not appear to have) – Jan 16 '17 at 07:41
@StephenMuecke it did have a property name `value` As stated in edit. Changing it was not the full sollution, so I added my solution, which worked. – Maciej Miśkiewicz Jan 16 '17 at 07:46
1

Cant see anything in your edit which suggest you have a property named `value` :) – Jan 16 '17 at 07:52

MVC view returning null value

2 Answers2