This seems like the model binding is causing me issues.

Essentially I have a model called ProductOption and for the purpose of this question it has 2 fields

ID (Int) PK ProductID (Int) FK

I have a standard route set-up

    context.MapRoute(
        "Product_default",
        "Product/{controller}/{action}/{id}",
        new { controller = "Product", action = "Index", id = UrlParameter.Optional }
    );

and if the user wants to add an option the URL is,

/Product/Options/Add/1

in the above URL 1 is the ProductID, I have the following code to return a blank model the the view,

[HttpGet]
public ActionResult Add(int id)
{
    return View("Manage", new ProductOptionModel() { ProductID = id });
}

Now in my view I keep a hidden field

<%= Html.HiddenFor(x=>x.ID) %>

This is used to determine (on submit) if we are editing or adding a new option. However the Model binder in .net seems to replace .ID (Which was 0 when leaving the above get actionresult) with 1 (or the value of the id parameter in the URL)

How can I stop or work around this?

ViewModel

public class ProductExtraModel
{
    //Database 
    public int ID { get; set; }
    public string Name { get; set; }
    public int ProductID { get; set; }

    public ProductModel Product { get; set; }
}