Question

I have a new MVC 4 Application with a fairly basic View/Controller. The associated Model contains a couple properties that I’ve mapped to Hidden form fields. When the Page renders the first time (e.g. via the HttpGet Action) it all looks fine. But when the form is Post’ed by selecting the Submit button the resulting Model presented to the Action no longer has the Hidden field values set. Here is a walkthrough of the particulars.

Here is a sample of the Model:

public class Application
{
    public bool ShowSideBars { get; set; }
}

Here is the initial Controller *Action* (which seems to work fine):

[HttpGet]
public ActionResult Application()
{
    var model = Request.ParseFromQueryString<Application>();
    model.ShowSideBars = true;

    return View(model);
}

This maps to the View as follows:

<fieldset>
    @Html.HiddenFor(m => m.ShowSideBars)
...
</fieldset>

This results in the following mark-up to be rendered inside the fieldset:

<input data-val="true" data-val-required="The ShowSideBars field is required." id="ShowSideBars" name="ShowSideBars" type="hidden" value="True" />

Note: I sure wish I knew why MVC has decided to add the ‘… field is required’ content when I didn’t flag it as required, but that’s for another question

Here is the Action that is called when the form is submitted. At this point the aforementioned property will no longer be set to ‘true‘.

[HttpPost]
public ActionResult Application(Application application)
{
    // Other work done here

    return View(application);
}

At present, there are no custom Model Binders. Also, I’ve tested some other data types and I’m seeing the same thing.

Can someone explain why hidden form values are not being returned? Am I just doing this all wrong?

Answer 1

I cannot reproduce the issue (ASP.NET MVC 4 Beta running on VS 2010 .NET 4.0).

Model:

public class Application
{
    public bool ShowSideBars { get; set; }
}

Controller:

public class HomeController : Controller
{
    public ActionResult Application()
    {
        var model = new Application();
        model.ShowSideBars = true;
        return View(model);
    }

    [HttpPost]
    public ActionResult Application(Application application)
    {
        return Content(application.ShowSideBars.ToString());
    }
}

View:

@model Application

@using (Html.BeginForm())
{
    @Html.HiddenFor(m => m.ShowSideBars)
    <button type="submit">OK</button>
}

When I submit the form, the model binder correctly assigns the ShowSideBars property in the POST action to true.

Note: I sure wish I knew why MVC has decided to add the ‘… field is
required’ content when I didn’t flag it as required, but that’s for
another question

That’s because non-nullable types such as booleans are always required. You could stop ASP.NET MVC helpers from emitting HTML5 data-* client side validation attributes for them by putting the following line in Application_Start:

DataAnnotationsModelValidatorProvider.AddImplicitRequiredAttributeForValueTypes = false;