我可以在自定义中间件中添加新的作用域服务吗? [英] Can I add a new scoped service within a custom middleware?

问题描述

我在Asp .Net Core中使用WebApi，我想知道是否/如何添加新的作用域服务，以便所有后续的中间件和控制器都可以通过依赖注入来访问?还是应该与HttpContext.Items共享状态?因为HttpContext在WebApi控制器中根本不可用，所以这似乎不是它的预期目的.

I'm using WebApi in Asp .Net Core and I'm wondering if/how I can add a new scoped service that all following middleware and controllers can get access to through dependency injection? Or should I share state with HttpContext.Items instead? That doesn't seem to be what it is intended for since HttpContext isn't available at all in a WebApi-controller?

如果HttpContext或DI都不是正确的工具，那么如何在不从头开始创建状态的情况下，在请求管道中传播状态呢?

If neither HttpContext or DI is the right tool for this, then how can I propagate state in the request-pipeline without having it already created from the beginning?

推荐答案

首先在您的ConfigureServices(IServiceCollection服务)中添加您的作用域服务

First add your scoped service in your ConfigureServices(IServiceCollection services)

services.AddScoped<IMyService, MyService>();

然后，我知道将范围服务注入到中间件中的唯一方法就是将其注入到Middlware的Invoke方法中

Then, the only way I know of to get a scoped service injected into your middleware is to inject it into the Invoke method of your Middlware

public class MyMiddleware
{
    private readonly RequestDelegate _next;

    public MyMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task Invoke(HttpContext httpContext, IMyService service)
    {
        service.DoSomething();
        await _next(httpContext);
    }
}

默认情况下，注入MyMiddleware的构造函数会使它成为单例，因为它仅在启动时被调用.每次都会调用Invoke，并且依赖项注入将获取作用域对象.

Injecting in the constructor of MyMiddleware will make it a singleton by default as it's only called on startup. Invoke is called every time and dependency injection will grab the scoped object.

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