MVC querystring parameter not passing through to action

Question

I have the following action:

public ActionResult CatchAll(string pathname, bool isPreview)
{
    CatchAllModel model = _aliasModelBuilder.BuildCatchAllModel(pathname, isPreview);

    if (model.Page != null)
    {
        return View(model);
    }
    else
    {
        throw new HttpException(404, "Page not found");
    }
}

And the route for this is

routes.MapRoute(
    name: "Default",
    url: "{*pathname}",
    defaults: new { controller = "Alias", action = "CatchAll", isPreview = false });

Now if I browse to localhost/about-us?isPreview=true , the pathname comes through as about-us but isPreview comes through as false.

Is there anything I'm doing wrong - I thought the route default should be overwritten by the query string

Answer 1

Ok this looks as if the default parameter set in the route is not being overwritten by the querystring. So I removed it from the route:

routes.MapRoute(
    name: "Default",
    url: "{*pathname}",
    defaults: new { controller = "Alias", action = "CatchAll" });

And added it to the action:

public ActionResult CatchAll(string pathname, bool isPreview = false)

I guess I'll have to suppress CA1026 as we can't make overload methods for actions