Set value of hidden value in mvc

Question

I pass a string parameter like this to a controller

    public ActionResult Index(string key="")
    {
        ViewBag.key = key;
        return View();
    }

And then I try to set it to a hidden value in the view. I tried 2 ways but none work.

                <input type="hidden" name="UniqueLink" id="UniqueLink" value="@ViewBag.key" />
                @Html.HiddenFor(u => u.UniqueLink,
                    new { id = "UniqueLink", Value = @ViewBag.key })

What am I doing wrong here? The values are never set at all. And if its set I need it to be available for the model when posting the form to this...

    public ActionResult Add(Core.Registration model)
    {

Maybe I have the complete wrong approach here...?

Answer 1

in controller :

public ActionResult Index(string key = "")
            {
                Registration registration = new Registration
                {
                    UniqueLink= key
                };
                return View(registration);
            }

in view :

@model Registration
@Html.HiddenFor(model => model.UniqueLink)