.net mvc html help ActionLink and parameters to controller class

Referring back to one of the comments:

I didn't discourage you from using HTML Helpers. I just meant the way you constructed the form and you used ActionLink was wrong. And it would be easier to just have an input for the product key inside the form, if that's the only thing you want to post back to the server.

And I would highly recommend you to read through documentations from Microsoft, at least this one: https://dotnet.microsoft.com/apps/aspnet/mvc to understand what a MVC is. From your code sample, I didn't see you used M - Model at all.

Anyway, if you just only want to get the product key the user types in, I would do it like this:

Define a Controller

I dislike the idea of putting everything under /home (i.e., HomeController). Just think about the URL to the page that would make sense to the user.

Now I am guessing what you are trying to do. I saw terms like product keys and trial keys. What about a controller called ProductKeyController:

public class ProductKeyController : Controller
{
    // This corresponds to /productkeys, and you can list all the product keys
    // on the view it returns.
    public ActionResult Index()
    {
        return View();
    }

    // This corresponds to /productkeys/create, and you can create a specific product
    // key by asking the user to provide a trial key?
    // The view this returns might be the page where you build the form
    public ActionResult Create()
    {
        ...
        return View();
    }

    // This corresponds the form post.
    [HttpPost]
    public ActionResult Create(CreateProductKeyViewModel model)
    {
        ...
        return View(model);
    }
}

The view model

Your MVC controller is responsible to fetch data, if needed, build a view model, and pass it to the view. When you create a product key, if you need to ask the user to enter anything, you can declare a model and properties within it:

public class CreateProductKeyViewModel
{
    [Required]
    [Display(Name = "Trial Key")]
    [MaxLength(22)]
    public string TrialKey { get; set; }
}

The View Create.cshtml

Since you know the controller will be passing the view model to the view, you can declare it on top of the view so that everything you do with the view model inside the view is strongly-typed.

@model CreateProductViewModel
@{
    Layout = "xxx";
}

<h1>Enter The Core-i Product Key (format RST 102A08R EPCA 00007)</h1>
@using(Html.BeginForm("create", "productKey", new { area = "" }, FormMethod.Post))
{
    @Html.LabelFor(x => x.TrialKey)
    @Html.TextBoxFor(x => x.TrialKey)

    <button type="submit">Create</button>
}

See how everything within the view is strongly-typed? You don't have to manually create the form and the input for asking user for the trial key.

And when the user enters the trial key and presses submit, it will post back to the Post method of Create. Since the view is declared with the view model, and the view model is the parameter of the create method, MVC has already done the model binding for you hence you will get what user entered on the post back.

This is at least something to get you started.

Note: I wrote everything by hand. Not tested.