Caliburn.Micro Application Bootstrapper to replace the default DI container with Autofac

app.xaml

<customBootstrapper:CaliburnAutofacApplication
    x:Class="MyApplication.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:MyApplication"
    xmlns:customBootstrapper="using:MyApplication.CustomBootstrapper">
</customBootstrapper:CaliburnAutofacApplication>

CaliburnAutofacApplication.cs

namespace MyApplication.CustomBootstrapper
{
    public abstract class CaliburnAutofacApplication : CaliburnApplication
    {
        protected IContainer Container;
        private readonly ContainerBuilder _builder;
        private FrameAdapter _rootFrame;

        protected CaliburnAutofacApplication()
        {
            _builder = new ContainerBuilder();
        }

        protected override void Configure()
        {
            HandleConfigure(_builder);

            Container = _builder.Build();
        }

        protected override object GetInstance(Type service, string key)
        {
            object instance;

            if (string.IsNullOrEmpty(key))
            {
                if (Container.TryResolve(service, out instance))
                {
                    return instance;
                }
            }
            else
            {
                if (Container.TryResolveNamed(key, service, out instance))
                {
                    return instance;   
                }
            }

            throw new Exception(string.Format("Could not locate any instances of service {0}.", service.Name));
        }

        protected override IEnumerable<object> GetAllInstances(Type service)
        {
            var result = Container.Resolve(typeof(IEnumerable<>).MakeGenericType(service)) as IEnumerable<object>;
            return result;
        }

        protected override void BuildUp(object instance)
        {
            Container.InjectProperties(instance);
        }

        protected override void PrepareViewFirst(Windows.UI.Xaml.Controls.Frame rootFrame)
        {
            _rootFrame = new FrameAdapter(rootFrame);
        }

        public virtual void HandleConfigure(ContainerBuilder builder)
        {
            builder.Register(x => _rootFrame).As<INavigationService>().SingleInstance();

            /* Register all types by default.  This will register the view models. */
            builder.RegisterAssemblyTypes(AssemblySource.Instance.ToArray()).AsSelf().InstancePerDependency();

            /* Personal classes to separate & manage the Autofac & Automapper configurations*/
            // AutofacConfiguration.Configure(builder);
            // AutomapperConfiguration.Configure(Container);
        }
    }    
}