Autofac：从SingleInstance'd类型引用到的Htt prequestScoped

问题描述

我有哪里的共享对象需要每个请求对象的引用的应用程序。

I've got an application where a shared object needs a reference to a per-request object.

Shared:      Engine
                |
Per Req:  IExtensions()
                |
             Request

如果我试图注入 IExtensions 直接进入引擎的构造函数，即使懒惰（中IExtension），我得到一个没有匹配的范围[请求]是其中要求该实例的范围是可见的。异常时，它会尝试实例每个 IExtension 。

If i try to inject the IExtensions directly into the constructor of Engine, even as Lazy(Of IExtension), I get a "No scope matching [Request] is visible from the scope in which the instance was requested." exception when it tries to instantiate each IExtension.

我如何创建的Htt prequestScoped实例，然后将其注入一个共享实例？

How can I create a HttpRequestScoped instance and then inject it into a shared instance?

难道被认为是很好的做法，将其设置在请求的厂（因此注入引擎进入 RequestFactory ）？

Would it be considered good practice to set it in the Request's factory (and therefore inject Engine into RequestFactory)?

推荐答案

由于发动机的使用寿命共享要求你不能注入请求范围的扩展了进去。你可能是发动机的方法或属性，将积极从目前的请求范围扩展解决的集合。

Due to the shared lifetime requirements of Engine you cannot inject request-scoped extensions into it. What you could have is a method or property on Engine that will actively resolve a collection of extensions from the current request scope.

因此​​，首先让引擎带构造依赖性：

So first, let Engine take a constructor dependency:

public class Engine
{
    public Engine(..., Func<IExtensions> extensionsPerRequest)
    {
        _extensionsPerRequest = extensionsPerRequest;
    }


    public IExtensions Extensions
    {
       get { return _extensionsPerRequest(); }
    }
 }

然后，在你的Autofac注册：

And then, in your Autofac registration:

builder.Register<Func<IExtensions>>(c => RequestContainer.Resolve<IExtensions>());

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