SignalR 2, Autofac, OWIN WebAPI will not pass message from server to hub

问题

I have tried several variations over the past several weeks and so far all I can do is pass a message from the UI to the server and back. I am unable to pass a message from my controller or other method outside the hub to the UI. It seems like I am not getting an instance of the HubContext. I've created a basic demo app from scratch and uploaded here:

https://github.com/cdecinkoKnight/SignalRDemo-help

I have a basic hub (MessageHub):

[HubName("messages")]
public class MessageHub : Hub, IMessageBroker
{
    public override Task OnConnected()
    {
        Debug.WriteLine("Connected: " + Context.ConnectionId);
        return base.OnConnected();
    }

    public void ShowNewMessage(string message)
    {
        Debug.WriteLine("Show New Message: " + message);

        Clients.All.showMessageOnPage("Show New Message: " + message);
    }
}

And a basic controller:

public class ValuesController : ApiController
{
    private readonly ISampleService _sampleService;
    private IConnectionManager _connectionManager;

    public ValuesController(ISampleService sampleService, IConnectionManager connectionManager)
    {
        _sampleService = sampleService;
        _connectionManager = connectionManager;
    }


    // GET api/values
    [HttpGet]
    public string Get()
    {
        var context = _connectionManager.GetHubContext<MessageHub>();
        context.Clients.All.showMessageOnPage("From controller");

        return _sampleService.GetDummyValue();
    }
}

I know the issue is in my Startup but so far nothing has worked.

public class Startup
{
    public void Configuration(IAppBuilder app)
    {
        var builder = new ContainerBuilder();

        builder.RegisterApiControllers(Assembly.GetExecutingAssembly());
        builder.RegisterHubs(Assembly.GetExecutingAssembly());

        builder.RegisterType<AutofacDependencyResolver>().As<IDependencyResolver>().SingleInstance();
        builder.RegisterType<ConnectionManager>().As<IConnectionManager>().SingleInstance();
        builder.RegisterType<SampleService>().As<ISampleService>().InstancePerLifetimeScope();
        builder.RegisterType<MessageBroker>().As<IMessageBroker>();

        var container = builder.Build();

        GlobalConfiguration.Configuration.DependencyResolver = new AutofacWebApiDependencyResolver(container);

        app.UseAutofacMiddleware(container);
        app.UseCors(CorsOptions.AllowAll);

        app.Map("/signalr", map =>
        {
            map.UseCors(SignalrCorsOptions.Value);
            map.UseAutofacMiddleware(container);

            var hubConfiguration = new HubConfiguration
            {
                Resolver = new AutofacDependencyResolver(container),
            };
            hubConfiguration.EnableDetailedErrors = true;
            hubConfiguration.EnableJavaScriptProxies = true;

            map.RunSignalR(hubConfiguration);
        });
    }

    private static readonly Lazy<CorsOptions> SignalrCorsOptions = new Lazy<CorsOptions>(() =>
    {
        return new CorsOptions
        {
            PolicyProvider = new CorsPolicyProvider
            {
                PolicyResolver = context =>
                {
                    var policy = new CorsPolicy();
                    policy.AllowAnyOrigin = true;
                    policy.Origins.Add("http://localhost:44386");
                    policy.AllowAnyMethod = true;
                    policy.AllowAnyHeader = true;
                    policy.SupportsCredentials = true;
                    return Task.FromResult(policy);
                }
            }
        };
    });
}

I'm hoping someone can take a look and help me get this working.

来源：https://stackoverflow.com/questions/65331998/signalr-2-autofac-owin-webapi-will-not-pass-message-from-server-to-hub