为什么autopac在httpRequest结束之前处理对象?

我正在编写一个ASP.NET MVC网站,使用autopac进行依赖项注入,Mindscape的Lightspeed作为ORM。有一个userrepository类,它依赖于Lightspeed UnitOfWork,以及哪个服务于登录控制器。

问题 :UnitOfWork在用户存储库完成使用之前被释放。

  public class UserRepository : IUserRepository
  {
    private readonly BluechipModelUnitOfWork _unitOfWork;

    public UserRepository(BluechipModelUnitOfWork unitOfWork)
    {
        _unitOfWork = unitOfWork;
    }
    public Principal GetPrincipal(string name)
    {
        // This line throws an ObjectDisposedException - UnitOfWork is already disposed.
        return _unitOfWork.Principals.FirstOrDefault(p => p.Name == name);
    }
    ...

在global.asax中,依赖关系连接如下:

public class MvcApplication : HttpApplication, IContainerProviderAccessor
{
    private static void RegisterAutofac()
    {
        var builder = new ContainerBuilder();

        // Register the lightspeed context as a singleton
        builder.RegisterInstance(new LightSpeedContext<BluechipModelUnitOfWork>("LightSpeedBluechip"))
            .As<LightSpeedContext<BluechipModelUnitOfWork>>()
            .SingleInstance();

        // Register the unit of work constructor so that a new instance is bound to each HttpRequest
        builder.Register(c => c.Resolve<LightSpeedContext<BluechipModelUnitOfWork>>().CreateUnitOfWork())
            .As<BluechipModelUnitOfWork>()
            .InstancePerLifetimeScope();

        // Register user repository to be one instance per HttpRequest lifetime
        builder.Register(c => new UserRepository(c.Resolve<BluechipModelUnitOfWork>()))
            .As<IUserRepository>()
            .InstancePerLifetimeScope();

        builder.Register(c => new CurrentUserService(
                                  c.Resolve<HttpSessionState>(),
                                  c.Resolve<IUserRepository>(),
                                  c.Resolve<IMembershipService>())
            ).As<ICurrentUserService>()
            .CacheInSession();

        builder.RegisterType<ExtensibleActionInvoker>().As<IActionInvoker>();
        builder.RegisterControllers(Assembly.GetExecutingAssembly()).PropertiesAutowired().InjectActionInvoker();
        builder.RegisterModelBinders(Assembly.GetExecutingAssembly());

        // Set the container provider up with registrations.    
        _containerProvider = new ContainerProvider(builder.Build());

        // Set the controller factory using the container provider.    
        ControllerBuilder.Current.SetControllerFactory(new AutofacControllerFactory(_containerProvider));

鉴于上述登记,为什么Autopac会处理UnitofWork?(