private async void FillPage() { List <OutputNotification> output_list = new List <OutputNotification>(); HttpResponseMessage response = await NotificationRequest.GetAllNotifications(); if (response.IsSuccessStatusCode) { string response_content = await response.Content.ReadAsStringAsync(); List <AppUserNotification> notifications_list = JsonConvert.DeserializeObject <List <AppUserNotification> >(response_content); foreach (AppUserNotification notification in notifications_list) { HttpResponseMessage responseOb = await ObservationRequest.GetObservationById(notification.Observation); if (responseOb.IsSuccessStatusCode) { string response_contentOb = await responseOb.Content.ReadAsStringAsync(); RequestObservation observation = JsonConvert.DeserializeObject <RequestObservation>(response_contentOb); if (observation != null) { OutputNotification output_value = new OutputNotification(observation, notification); output_list.Add(output_value); } } else { if (response.StatusCode == System.Net.HttpStatusCode.BadGateway) { await DisplayAlert("Attention!!!", "No connection with the server", "OK"); } if (response.StatusCode == System.Net.HttpStatusCode.BadRequest) { await DisplayAlert("Try Again!", "Invalid request", "OK"); } } } Notifications = output_list; MyCollectionView.ItemsSource = Notifications; } else { if (response.StatusCode == System.Net.HttpStatusCode.BadGateway) { await DisplayAlert("Attention!!!", "No connection with the server", "OK"); } if (response.StatusCode == System.Net.HttpStatusCode.BadRequest) { await DisplayAlert("Try Again!", "Invalid request", "OK"); } } }