Dynamicweb Razor redirect if missing PID

redirectIfPIDMissing.cshtml

// Code snippet for request missing PID - say coming from Google search
@using System.Web
@using Dynamicweb.Frontend;

var request = HttpContext.Current.Request;
var response = HttpContext.Current.Response;

var pidFromRequest = Dynamicweb.Base.ChkString(request["pid"]);
var pageviewURL = GetGlobalValue("Global:Pageview.Url");
if (pidFromRequest=="") {
    pageviewURL+= (pageviewURL.IndexOf("?")==-1) ? "?" : "&";
    pageviewURL+="pid="+PID.ToString();
    response.RedirectPermanent(pageviewURL, true);
}