Question

I’ve a form in which I only have to choose between several entities.

So here is what I’ve done:

Created a view Model:

    public class EntityChooserModel
    {
        public IEnumerable<Entity> AvailableEntities { get; set; }
        public int SelectedId;
    }

I’ve two actions in the controller, one with [HTTPPost], one without. In both I have a “SessionUserData”, which is session data, bound through data model binding.

        [Authorize]
        public ActionResult EntityChooser(SessionUserData sessionData)
        {
            List<Entity> entities = _userStore.GetRoles(User.Identity.Name).Select(ur => ur.Entity).ToList();


            Entity entity = sessionData.IdCurrentEntity != null ? entities.Where(e => e.Id == sessionData.IdCurrentEntity).First() : entities.First();

            return View(new EntityChooserModel() { SelectedId = entity.Id, AvailableEntities = entities });
        }

.

    [Authorize]
    [HttpPost]
    public ActionResult EntityChooser( EntityChooserModel model, SessionUserData sessionData, String returnUrl)
    {
        if (ModelState.IsValid)
        {
            Entity entity = _userStore.GetRoles(User.Identity.Name).Select(ur => ur.Entity).Where(e => e.Id == model.SelectedId).First();
            sessionData.IdCurrentEntity = entity.Id;
            RedirectToDefaultPage(returnUrl);
        }
        return View(model);
    }

And the strongly typed view:

@model My.Full.Namespace.EntityChooserModel
@{
    ViewBag.Title = "EntityChooser";
    Layout = "~/Views/Shared/_LoginLayout.cshtml";
}
<div id="login-wrapper">
    <div id="title">
        <h1>Login</h1>
    </div>
    <div id="login">
        @using (Html.BeginForm("EntityChooser", "Auth", FormMethod.Post, new { id = "ChooseFormId" }))
        {            
            @Html.ValidationSummary(true, "Loggin error")
            <div>
                <span>Choose an entity:</span>
                @Html.DropDownListFor(x => x.SelectedId, new SelectList(Model.AvailableEntities, "Id", "Name"))
            </div>
            <p class="right-aligned">
                <a href="javascript:document.getElementById('ChooseFormId').submit();" class="adm-button">
                    <span class="next-btn"><span>Select</span></span></a>
            </p>
            <input type="submit" style="display: none" />
        }
    </div>
</div>

The problem is that when I receive the data in the second model, I’ve an empty object. The collection is empty, and the id is set to the default value(0).

What is wrong? I can’t find out what I missed on this one.

It’s the first time I do an mvc form which isn’t ForModel(), and the first time I’ve to use a dropdownlist

Answer 1

The only input element that your <form> contains is a single drop down list which sends only the selected value to the server when POSTed. This explains why your AvailableEntities collection property is empty.

As far as why the SelectedId field is empty, it is because you have defined it as a field and not as a property. The default model binder works only with properties. So if you want it to be populated you must define it as a property:

public int SelectedId { get; set; }

As far as the AvailableEntities property is concerned you could populate it from your repository in the POST action using the selected id.