protected override async void OnNavigatedTo(NavigationEventArgs e)
{
//base.OnNavigatedTo(e);
GatewayList = new ObservableCollection<OneServerInfo>();
GatewayAdded = new ConcurrentDictionary<String, OneServerInfo>(StringComparer.OrdinalIgnoreCase);
ViewOfGateway.ItemsSource = this.GatewayList;
LastGateway = null;
SelectedIndexValue = 0;
var scaleFactor = DisplayInformation.GetForCurrentView().RawPixelsPerViewPixel;
var ScreenHeight = Window.Current.Bounds.Height;
var DeviceHeight = ScreenHeight * scaleFactor;
NumberItemShowed = (int)Math.Floor((ScreenHeight - 220.0) / 60.0 + 0.5);
MinItemShowed = 0;
var currentApp = (App)App.Current;
OldGateway = currentApp.CurrentGateway;
var nRet = await UpdateGatewayInfo();
this.navigationHelper.OnNavigatedTo(e);
}