Webview Navigation events not firing on iOS

Hi i have using following code working fine android but not get response from iOS in xamarin forms

         public async void WebViewnavigated(WebNavigatedEventArgs args, NavigationEventArgs e, string url)
            {
                try
                {
                    var obj = Newtonsoft.Json.JsonConvert.SerializeObject(web_view_login.Source);
                    var uri = Newtonsoft.Json.JsonConvert.DeserializeObject<JObject>(obj)["Url"];


                    var access_token = uri.ToString();

                    if (access_token.Contains("access_token"))
                    {
                        var accesstoken_ = uri.ToString().Split(new char[] { '?', '&', '{', '}', '=' })[2];
                        var token_type = uri.ToString().Split(new char[] { '?', '&', '{', '}', '=' })[4];
                        await Navigation.PushAsync(new Home());
                        //await Navigation.PopAsync();
                    }
                }
                catch (Exception ex)
                {

                }

            }