asp.net - 解析 ASP.NET 后台任务中的 Autofac 组件

Question

在 ASP.NET 中使用 Autofac 以及 ContainerDisposalModule，我如何支持具有需要解决的组件依赖性的即发即忘调用？我遇到的问题是 ASP.NET 请求在运行任务之前完成并处理请求的生命周期范围，因此需要在新线程中解析的任何组件都会失败，并显示消息“实例无法解析”并且无法从此 LifetimeScope 创建嵌套生命周期，因为它已被释放”。在 ASP.NET 中使用 Autofac 支持即发即忘调用的最佳方式是什么？我不想延迟执行某些可以在后台线程上完成的任务的请求。

Answer 1

Alex 发布的答案适用于当前的 Autofac 和 MVC 版本:

• 使用 InstancePerRequest 作为数据库上下文
• 添加 ILifetimeScope 作为依赖项以访问容器
• SingleInstance 确保它是根生命周期范围
• 使用HostingEnvironment.QueueBackgroundWorkItem可靠在后台运行某些内容
• 使用 MatchingScopeLifetimeTags.RequestLifetimeScopeTag 来避免必须知道 autofac 用于 PerRequest 生命周期的标记名

https://groups.google.com/forum/#!topic/autofac/gJYDDls981A https://groups.google.com/forum/#!topic/autofac/yGQWjVbPYGM

要点:https://gist.github.com/janv8000/35e6250c8efc00288d21

Global.asax.cs:

protected void Application_Start() {
  //Other registrations
  builder.RegisterType<ListingService>();
  builder.RegisterType<WebsiteContext>().As<IWebsiteContext>().InstancePerRequest();  //WebsiteContext is a EF DbContext
  builder.RegisterType<AsyncRunner>().As<IAsyncRunner>().SingleInstance();
}

AsyncRunner.cs

public interface IAsyncRunner
{
    void Run<T>(Action<T> action);
}

public class AsyncRunner : IAsyncRunner
{
    public ILifetimeScope LifetimeScope { get; set; }

    public AsyncRunner(ILifetimeScope lifetimeScope)
    {
        Guard.NotNull(() => lifetimeScope, lifetimeScope);
        LifetimeScope = lifetimeScope;
    }

    public void Run<T>(Action<T> action)
    {
        HostingEnvironment.QueueBackgroundWorkItem(ct =>
        {
            // Create a nested container which will use the same dependency
            // registrations as set for HTTP request scopes.
            using (var container = LifetimeScope.BeginLifetimeScope(MatchingScopeLifetimeTags.RequestLifetimeScopeTag))
            {
                var service = container.Resolve<T>();
                action(service);
            }
        });
    }
}

Controller

public Controller(IAsyncRunner asyncRunner)
{
  Guard.NotNull(() => asyncRunner, asyncRunner);
  AsyncRunner = asyncRunner;
}

public ActionResult Index()
{
  //Snip
  AsyncRunner.Run<ListingService>(listingService => listingService.RenderListing(listingGenerationArguments, Thread.CurrentThread.CurrentCulture));
  //Snip
}

列表服务

public class ListingService : IListingService
{
  public ListingService(IWebsiteContext context)
  {
    Guard.NotNull(() => context, context);
    Context = context;
  }
}