Asp.net核心如何注册也包含自定义接口的IHostedService [英] Asp.net core How to Register IHostedService which also Contains a Custom Interface

问题描述

如何属性注册一个同时包含 IHostedService 和自定义接口(例如 IMyInterface )的类?

How do I property register an class which contains both the IHostedService and a custom interface like IMyInterface?

与

Class BackgroundTaskScheduler类:BackgroundService，ITaskScheduler {...}

如果配置如下:

services.AddHostedService<BackgroundTaskScheduler>();

然后尝试将其注入客户端，如下所示:

And then try to have it inject into a client, like so:

public class Foo
{
    Foo(ITaskScheduler taskScheduler) {...}
}

生成错误，表明ASP.net无法解析 BackgroundTaskScheduler ，为什么?

An error is generated stating that ASP.net can't resolve BackgroundTaskScheduler, why?

推荐答案

阅读了很多想法之后，包括:

After reading lots of ideas, including:

• AddHostedService()将服务注册为临时服务-我同意大多数抱怨，因为大多数托管服务不是独立存在和/或运行的.
• 如何注入对特定IHostedService的引用实施?-提出了一个独特的概念，即使用隐藏的 HostedServicewrapping 类将启动和停止调用转发到真正的托管服务.

• AddHostedService() registers service as Transient - which I agree with most of the complains, since most hosted services don't live and/or run in isolation.
• How to inject a reference to a specific IHostedService implementation? - which suggested a unique concept of using a hidden HostedServicewrapping class which forward the start and stop calls to the real hosted service.

但是，如何在不需要包装类的情况下使其工作呢?我将上面讨论的想法结合到以下两种扩展方法中.

But how to get it to work without requiring a wrapper class? I combined the ideas discussed above into the following two extension methods.

如果您喜欢使用接口DI，如 Bar.Bar(IFoo foo)中所示，请使用以下代码:

If you like using interface DI, as in Bar.Bar(IFoo foo) then use this one:

        /// <summary>
        /// Used to register <see cref="IHostedService"/> class which defines an referenced <typeparamref name="TInterface"/> interface.
        /// </summary>
        /// <typeparam name="TInterface">The interface other components will use</typeparam>
        /// <typeparam name="TService">The actual <see cref="IHostedService"/> service.</typeparam>
        /// <param name="services"></param>
        public static void AddHostedApiService<TInterface, TService>(this IServiceCollection services)
            where TInterface : class
            where TService : class, IHostedService, TInterface
        {
            services.AddSingleton<TInterface, TService>();
            services.AddSingleton<IHostedService>(p => (TService) p.GetService<TInterface>());
        }

用法:

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddHostedApiService<ITaskScheduler, BackgroundTaskScheduler>();
        }

具体的类依赖注入

如果您想使用具体的类注入，如 Bar.Bar(Foo foo)中所示，请使用:

        /// <summary>
        /// Used to register <see cref="IHostedService"/> class which defines an interface but will reference the <typeparamref name="TService"/> directly.
        /// </summary>
        /// <typeparam name="TService">The actual <see cref="IHostedService"/> service.</typeparam>
        public static void AddHostedApiService<TService>(this IServiceCollection services)
            where TService : class, IHostedService
        {
            services.AddSingleton<TService>();
            services.AddSingleton<IHostedService>(p => p.GetService<TService>());
        }

用法:

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddHostedApiService<BackgroundTaskScheduler>();
        }

享受！

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