asp.net-mvc - 在 MVC 5 应用程序中使用 autofac 注入(inject) SignalR Hub 的依赖项

Question

我正在尝试将 SignalR 2 引入现有项目，其中所有依赖项注入(inject)均使用 autofac 执行，所有依赖项配置均在 Global.asax 中执行。我找到了 Autofac.SignalR 包，用于将 SignalR 与 autofac 一起使用及其 accompanying documentation .

我按照提供的文档中的示例进行操作，并遵循使用 RegisterHubs 函数的建议，而不是定义我个人的集线器依赖项。

不幸的是，我的 Hub 类在尝试解析生命周期范围的依赖项时出现以下运行时错误

Autofac.Core.DependencyResolutionException was unhandled by user code
HResult=-2146233088
Message=No scope with a Tag matching 'AutofacWebRequest' is
visible from the scope in which instance was requested.
This generally indicates that a component registered as per-HTTP
request is being requested by a SingleInstance() component
(or a similar scenario.) Under the web integration always request
dependencies from the DependencyResolver.Current or 
ILifetimeScopeProvider.RequestLifetime, never from the container itself.

我无法让 DependencyResolver.Current 或 ILifeTimeScopeProvider 为我工作。

我的依赖配置如下

var builder = new ContainerBuilder();
    .RegisterControllers(typeof (MvcApplication).Assembly);
    .RegisterHubs(Assembly.GetExecutingAssembly());
    ...
var container = builder.Build();

// Set dependency resolver for MVC
DependencyResolver.SetResolver(new AutofacDependencyResolver(container));

// Set dependency resolver for Web API
GlobalConfiguration.Configuration.DependencyResolver = new AutofacWebApiDependencyResolver(container);

// Set the dependency resolver for SignalR
DependencyResolver.SetResolver(new AutofacDependencyResolver(container));

var signalRDependencyResolver = new Autofac.Integration.SignalR.AutofacDependencyResolver(container);
GlobalHost.DependencyResolver = signalRDependencyResolver;

我还根据示例设置了我的集线器类:

public class BaseHub : Hub
{
    protected readonly ILifetimeScope _hubLifetimeScope;
    private static IUserSignalRConnectionRepository _userSignalRConnectionRepository;

    public BaseHub(ILifetimeScope lifetimeScope) : base()
    {
        _hubLifetimeScope = lifetimeScope.BeginLifetimeScope();

        _userSignalRConnectionRepository = _hubLifetimeScope.Resolve<IUserSignalRConnectionRepository>();
    }

    protected override void Dispose(bool disposing)
    {
        // Dipose the hub lifetime scope when the hub is disposed.
        if (disposing && _hubLifetimeScope != null)
            _hubLifetimeScope.Dispose();

        base.Dispose(disposing);
    }
}

异常发生在线上的cub类

_userSignalRConnectionRepository = _hubLifetimeScope.Resolve<IUserSignalRConnectionRepository>();

Answer 1

您应该包含注册 IUserSignalRConnectionRepository 的代码。

错误消息似乎表明此依赖项是使用 InstancePerHttpRequest() 注册的，这相当于 InstancePerMatchingLifetimeScope("AutofacWebRequest")。对于 MVC 请求，会自动为您创建此范围，但对于 SignalR 请求则不会(这可能是一件好事，因为它们可以无限期地持续)。

您可以通过调用 lifetimeScope.BeginLifetimeScope("AutofacWebRequest"); 来解决此问题。而不是 Hub 构造函数中的 lifetimeScope.BeginLifetimeScope();。

或者，您可以使用 InstancePerDependency()(默认设置)或 SingleInstance() 而不是 InstancePerHttpRequest() 来注册 IUserSignalRConnectionRepository。