void Current_VisibilityChanged(object sender, Windows.UI.Core.VisibilityChangedEventArgs e)
{
Window.Current.VisibilityChanged -= Current_VisibilityChanged;
rootFrame = Window.Current.Content as Frame;
if (rootFrame != null)
{
SubscribeEvents();
}
else if (Window.Current.Content != null)
ErrorRootIsNotFrame();
}