private async Task Save() { string setting_obj = ""; if (File.Exists(Globals.app_setting_json)) { File.Delete(Globals.app_setting_json); } if (ValidateInput()) { app_setting = new AppSetting { device_id = DeviceId, api_endpoint = API_endpoint, api_entity = API_entity, api_url = API_url }; setting_obj = JsonConvert.SerializeObject(app_setting); JObject obj = JObject.Parse(setting_obj); using (StreamWriter file = File.CreateText(Globals.app_setting_json)) using (JsonTextWriter writer = new JsonTextWriter(file)) { obj.WriteTo(writer); } ResetValues(); if (Load()) { await _nav.DisplayAlert("Settings", "Settings has been saved and loaded.", "OK"); } } }