在应用程序启动中初始化structuremap容器,但在应用程序beginrequest中为空

在我的webapi应用程序中,我试图初始化 IContainer 在里面 Application_Start 储存在 _container 领域:

public class WebApiApplication : System.Web.HttpApplication
{
    private IContainer _container;

    public IContainer Container
    {
        get => (IContainer)HttpContext.Current.Items[nameof(Container)];
        set => HttpContext.Current.Items[nameof(Container)] = value;
    }

    protected void Application_Start()
    {
        _container = new Container(_ => _.Scan(scan =>
        {
            scan.TheCallingAssembly();
            scan.WithDefaultConventions();
            scan.With(new ControllerConvention());
        }));

        AreaRegistration.RegisterAllAreas();
        GlobalConfiguration.Configure(WebApiConfig.Register);
        FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
        RouteConfig.RegisterRoutes(RouteTable.Routes);
        BundleConfig.RegisterBundles(BundleTable.Bundles);
        DependencyResolver.SetResolver(new StructureMapDependencyResolver(() => 
            Container ?? _container.GetNestedContainer()));


    }

    public void Application_BeginRequest() =>
        Container = _container.GetNestedContainer();

    public void Application_EndRequest()
    {
        Container.Dispose();
        Container = null;
    }
}

在调试时,介于 Application_Start() 以及 Application_BeginRequest() , the 容器,容器 场变成 null .

我在这里做错什么了?