Request.IsAjaxRequest() alternative in MVC6

I am trying to run this example Rendering Partial Views using ajax, but i got the following compilation error:

'HttpRequest' does not contain a definition for 'IsAjaxRequest' and no extension method 'IsAjaxRequest' accepting a first argument of type 'HttpRequest' could be found.

    public ActionResult ItemsList(string ID)
    {
        Item item = Service.GetItemById(ID);

        if (Request.IsAjaxRequest())
        {
            return PartialView("viewPath", item);
        }
        else
        {
            return View("viewPath", item);
        }
    }

Check the user agent, as this:

var isAjax = Request.Headers["X-Requested-With"] == "XMLHttpRequest"
           || Request.Headers["X-Requested-With"] == "Fetch";