Xamarin Prism Unable to navigate to LoginPageViewModel - xamarin

Question

I am trying to make my Xamarin Project use MVVM with Prism and DryIoc.
I mostly want to use AutoRegistration like below:
[AutoRegisterForNavigation]
...
protected override void RegisterTypes(IContainerRegistry containerRegistry)
{
//Pages
containerRegistry.RegisterForNavigation<NavigationPage>();
//Services
containerRegistry.RegisterSingleton<ILocalDatabase, LocalDatabase>();
containerRegistry.RegisterSingleton<IUserProfileDataStore, UserProfileDataStore>();
containerRegistry.RegisterSingleton<IApplicationSettings, ApplicationSettings>();
containerRegistry.RegisterSingleton<ILogger, Logger>();
containerRegistry.RegisterSingleton<IApiService, ApiService>();
containerRegistry.RegisterSingleton<IUserSession, UserSession>();
containerRegistry.Register<IBrowser, BrowserImplementation>();
containerRegistry.Register<IConnectivity, ConnectivityImplementation();
containerRegistry.Register<IFileSystem, FileSystemImplementation>();
containerRegistry.Register<ICoreServices, CoreServices>();
}
I have also tried Manual Registration:
containerRegistry.RegisterForNavigation<LoginPage, LoginPageViewModel>();
Neither works, It hits the Login Page code behind then breaks with the following error:
Exception - High: Prism.Ioc.ContainerResolutionException:
An unexpected error occurred while resolving 'AppetiteApp.ViewModels.LoginPageViewModel' --->
DryIoc.ContainerException: code: UnableToResolveUnknownService; message: Unable to resolve
Resolution root AppetiteApp.ViewModels.LoginPageViewModel
with passed arguments [value(Prism.Navigation.ErrorReportingNavigationService)]
**System.NullReferenceException:** 'Object reference not set to an instance of an object.'
I've also tried using a Linker file setting it's build action to "linkdescription"
As for my Login Page here is the declaration
public LoginPageViewModel(ICoreServices coreServices)
: base(coreServices)

Answer 1

The constructor of LoginPageViewModel requires the ICoreServices argument which is registered.
The error message says that the LoginPageViewModel itself is unknown to the IoC - it means the type LoginPageViewModel is not directly registered and not found through dynamic registrations or unknown service resolvers.
I am not a user of the Xamarin Prism so I am not sure about its mechanism for registering the view models.
Btw, this part of error
Resolution root AppetiteApp.ViewModels.LoginPageViewModel
with passed arguments [value(Prism.Navigation.ErrorReportingNavigationService)]
basically means the view-model was resolved via the foollowing call resolver.Resolve(typeof(LoginPageViewModel), args: new[] { errorReportingNavigationService })
Hope it will help you or someone knowledgeable in Xamarin to track the error cause.

Answer 2

So Once I investigated Inside of ICoreServices I commented out each of the dependencies then discovered that IUserSession was the once causing problems then I dug into that and discovered that the dependences for IAppInfo and IVersionTracking were missing in the App.Xaml.cs registr tyepes so I added that and then it worked!
containerRegistry.Register<IAppInfo, AppInfoImplementation>();
containerRegistry.Register<IVersionTracking, VersionTrackingImplementation>();