Cannot create my custom navigation service wrapper

[ste8]

Hello,
I'd like to create a wrapper to Uno's Navigator, in order to expose only some methods.

So I defined my custom navigation service in this way:

public interface IMyNavigationService
{
    Task<NavigationResponse?> NavigateViewModelAsync<T>(object sender);
}

public class MyNavigationService : IMyNavigationService
{
    private readonly INavigator _navigator;

    public MyNavigationService(INavigator navigator)
    {
        _navigator = navigator;
    }

    public async Task<NavigationResponse?> NavigateViewModelAsync<T>(object sender)
    {
        return await _navigator.NavigateViewModelAsync<T>(this);
    }
}

then I've registered it as

.ConfigureServices((context, services) =>
{
    services.AddSingleton<IMyNavigationService, MyNavigationService>();
})

and finally in the ViewModel I've injected it instead of INavigator.

But when I try to navigate to the second page, I get the error

"System.ArgumentNullException: Value cannot be null. (Parameter 'provider')
at System.ThrowHelper.Throw(String paramName)
at System.ThrowHelper.ThrowIfNull(Object argument, String paramName)
at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider)
at Uno.Extensions.Navigation.NavigatorExtensions.GetResolver(INavigator navigator)
at Uno.Extensions.Navigation.NavigatorExtensions.NavigateRouteHintAsync(INavigator navigator, RouteHint routeHint, Object sender, Object data, CancellationToken cancellation)
at Uno.Extensions.Navigation.NavigatorExtensions.NavigateViewModelAsync(INavigator navigator, Object sender, Type viewModelType, String qualifier, Object data, CancellationToken cancellation)
at Uno.Extensions.Navigation.NavigatorExtensions.NavigateViewModelAsync[TViewViewModel](INavigator navigator, Object sender, String qualifier, Object data, CancellationToken cancellation)
at UnoAppCustomNav.Ser
vices.MyNavigati..."

What am I doing wrong?

I saw in Uno.Extensions' code that INavigator is registered in several points as 'AddScopedInstance' instead of singleton. Can the issue depends from that?
Actually I didn't fully understand what ScopedInstance means in the context of Uno, is there any documentation about that?

[nickrandolph]

@ste8 I think if you register the MyNavigationService using AddScopedInstance this should address this issue.

Scoping is used as a way of keeping multiple navigation stacks independent from each other. For example if you have a Frame that has a navigation stack (similar to the Frame's backstack) but then within any of those pages you might have a TabBar which has it's own navigation stack.

We create a new scope for each navigation region, so you'll get a different INavigator for each navigation region. INavigators aren't related to each other, but do map to a navigation region, and navigation regions are typically part of a hierarchy defined by the application flow.

[ste8]

Thanks @nickrandolph , I tried in several ways to register the service using "AddScopedInstance", but none of them worked.

AddScopedInstance takes only one type as argument, which one should I specify, MyNavigationService or IMyNavigationService ?