在 MVC 5 应用程序中使用 autofac 为 SignalR Hub 注入依赖项

Question

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

我遵循了提供的文档中的示例，并遵循了使用 RegisterHubs 函数而不是定义我的个人集线器依赖项的建议。

不幸的是，我的 Hub 类在尝试解决来自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;

我也按照例子设置了我的hub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cub类就行了

_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，相当于InstancePerMatchingLifetimeScope("AutofacWebRequest")。这个范围是在 MVC 请求的情况下为您自动创建的，但不是为 SignalR 请求创建的（这可能是一件好事，因为它们可以无限期地持续下去）。

您可以通过调用lifetimeScope.BeginLifetimeScope("AutofacWebRequest"); 来解决这个问题。而不是您的 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。