Xamarin.ios MVVMLight的导航问题

在尝试使用MVLight导航时，我遇到了几个问题

在iOS上，我使用以下代码在AppDelegate/FinishedLoading中创建了导航服务

        var nav = new NavigationService();

        nav.Configure(ViewModelLocator.MainPageKey, "MainPage");
        nav.Configure(ViewModelLocator.MapPageKey, "MapPage");

        // iOS uses the UINavigtionController to move between pages, so will we
        nav.Initialize(Window.RootViewController as UINavigationController);

        // finally register the service with SimpleIoc
        SimpleIoc.Default.Register<INavigationService>(() => nav);

我的导航线是这样的

INavigationService navigationService;
...code
navigationService.NavigateTo(ViewModelLocator.MapPageKey, new List<double> { Latitude, Longitude });

INavigationService导航服务；
…代码
navigationService.NavigateTo（ViewModelLocator.MapPageKey，新列表{纬度，经度}）；

这把我难住了

UNHANDLED EXCEPTION:
[MonoDroid] System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> Microsoft.Practices.ServiceLocation.ActivationException: Type not found in cache: System.Object.

INavigationService navigationService;
...code
navigationService.NavigateTo(ViewModelLocator.MapPageKey, new List<double> { Latitude, Longitude });