Autofact, MakeGenericMethod.Invoke not working

I tried to use autofac IRegistrationSource resolve other interface,but it's not working. Below is my code:
public class SettingsSource : IRegistrationSource { static readonly MethodInfo BuildMethod = typeof(SettingsSource).GetMethod( "BuildRegistration", BindingFlags.Static | BindingFlags.NonPublic);

    public IEnumerable<IComponentRegistration> RegistrationsFor(
            Service service,
            Func<Service, IEnumerable<IComponentRegistration>> registrations)
    {
        var ts = service as TypedService;
        if (ts != null && typeof(ISettings).IsAssignableFrom(ts.ServiceType))
        {
            var buildMethod = BuildMethod.MakeGenericMethod(ts.ServiceType);
            yield return (IComponentRegistration)buildMethod.Invoke(null, null);
        }
    }

    static IComponentRegistration BuildRegistration<TSettings>()
        where TSettings : ISettings, new()
    {
        return RegistrationBuilder
            .ForDelegate((c, p) =>
            {
                return c.Resolve<ISettingService>().LoadSetting<TSettings>();
            })
            .InstancePerLifetimeScope()
            .CreateRegistration();
    }

    public bool IsAdapterForIndividualComponents { get { return false; } }
}

method BuildRegistration can't be fired.

I checked bellow links, still can't figure out why. Autofac. How to use custom method(property) to resolve some interface?

http://ift.tt/1ITIiIn

anyone can give a clue?

Thanks