private void setup()
{
var ns = new NavigationService(this, Resource.Id.content_frame);
navService = ns;
ns.RegisterFragment<ISettingsViewModel, SettingsFragment>();
ns.RegisterFragment<ILoginViewModel, LoginFragment>();
ns.RegisterFragment<IHomeViewModel, HomeFragment>();
ViewModelLocator.Container.RegisterInstance<INavigationService>(navService);
var container = ViewModelLocator.Container;
ISharedPreferences prefs = PreferenceManager.GetDefaultSharedPreferences(this);
var settings = new AppSettings(prefs);
settings.ServerUrl = null;
container.RegisterInstance<ISettings>(settings);
vm = container.Resolve<IShellViewModel>();
vm.PropertyChanged += vmPropertyChanged;
}