EPiServer - Set Root Page Restrictions

 [InitializableModule]
    [ModuleDependency(typeof(EPiServer.Web.InitializationModule))]
    public class RootPageRestrictions : IInitializableModule
    {
        public void Initialize(InitializationEngine context)
        {
            var typeRepo = ServiceLocator.Current.GetInstance<IContentTypeRepository>();
            var sysRoot = typeRepo.Load("SysRoot") as PageType;


            var setting = new AvailableSetting {Availability = Availability.Specific};
            setting.AllowedContentTypeNames.Add(startPage.Name);
            setting.AllowedContentTypeNames.Add(settingsPage.Name);

            var availabilityRepository = ServiceLocator.Current.GetInstance<IAvailableSettingsRepository>();
            availabilityRepository.RegisterSetting(sysRoot, setting);

        }

        public void Preload(string[] parameters) { }

        public void Uninitialize(InitializationEngine context)
        {
            //Add uninitialization logic
        }
    }