Html.HiddenFor value property not getting set

The following will work in MVC 4

@Html.HiddenFor(x => x.CRN, new { @Value = "1" });

@Value property is case sensitive. You need a capital 'V' on @Value.

Here is my model

public int CRN { get; set; }

Here is what is output in html when you look in the browser

<input value="1" data-val="true" data-val-number="The field CRN must be a number." data-val-required="The CRN field is required." id="CRN" name="CRN" type="hidden" value="1"/>

Here is my method

[HttpPost]
public ActionResult MyMethod(MyViewModel viewModel)
{
  int crn = viewModel.CRN;
}

Have you tried using a view model instead of ViewData? Strongly typed helpers that end with For and take a lambda expression cannot work with weakly typed structures such as ViewData.

Personally I don't use ViewData/ViewBag. I define view models and have my controller actions pass those view models to my views.

For example in your case I would define a view model:

public class MyViewModel
{
    [HiddenInput(DisplayValue = false)]
    public string CRN { get; set; }
}

have my controller action populate this view model:

public ActionResult Index()
{
    var model = new MyViewModel
    {
        CRN = "foo bar"
    };
    return View(model);
}

and then have my strongly typed view simply use an EditorFor helper:

@model MyViewModel
@Html.EditorFor(x => x.CRN)

which would generate me:

<input id="CRN" name="CRN" type="hidden" value="foo bar" />

in the resulting HTML.