Passing an interface in Shell

gistfile1.txt

I fire up my forms app with the following

(From https://github.com/CrossGeeks/SocialMediaAuthenticationSample - the services etc are implemented on the platform)

LoadApplication(new App(new OAuth2Service()));

My app.xaml.cs looks like this

public App(IOAuth2Service oAuth2Service)
{
    // stuff
    
  MainPage = new AppShell();
  Shell.Current.GoToAsync($"//Login?Auth={oAuth2Service}");
}

I have in my AppShell.xaml the following

    <ShellItem Route="Login">
        <ShellContent ContentTemplate="{DataTemplate local:LoginPage}" />
    </ShellItem>
    
And finally in my LoginPage

IOAuth2Service  auth;
        public IOAuth2Service Auth
        {
            get => auth;
            set
            {
                auth = value;
                OnPropertyChanged();
            }
        }
        
 When I run the app and check the Auth property, it's null. 
 
 Do I need to remove this route from AppShell.xaml or is there something I'm missing?