BVNetwork.NotFound.Core.NotFoundPage.NotFoundPageUtil.GetReferer C# (CSharp) Method

        public static string GetReferer(HttpRequestBase request)
        {
            string referer = request.ServerVariables["HTTP_REFERER"];
            if (referer != null)
            {
                // Strip away host name in front, if local redirect
                string hostUrl = SiteDefinition.Current.SiteUrl.ToString();
                if (referer.StartsWith(hostUrl))
                    referer = referer.Remove(0, hostUrl.Length);
            }
            else
                referer = ""; // Can't have null
            return referer;
        }

        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            if (PageEditing.PageIsInEditMode)
            {
                return;
            }

            Logger.Debug("Starting 404 handler action filter");
            var request = filterContext.HttpContext.Request;

            filterContext.HttpContext.Response.TrySkipIisCustomErrors = true;
            var statusCode = NotFoundPageUtil.GetStatusCode(request);

            filterContext.HttpContext.Response.StatusCode = statusCode;
            var status = NotFoundPageUtil.GetStatus(statusCode);

            if (!string.IsNullOrEmpty(status))
            {
                filterContext.HttpContext.Response.Status = status;
            }
            NotFoundPageUtil.SetCurrentLanguage(filterContext.HttpContext);
            filterContext.Controller.ViewBag.Referrer    = NotFoundPageUtil.GetReferer(request);
            filterContext.Controller.ViewBag.NotFoundUrl = NotFoundPageUtil.GetUrlNotFound(request);
            filterContext.Controller.ViewBag.StatusCode  = statusCode;
        }