.net核心3依赖项注入服务作为“配置"的参数

问题描述：

我刚刚将.net核心应用程序从2.2版升级到了3版. 在startup.cs的ConfigureServices方法内部，我需要解析身份验证服务使用的服务. 我正在使用"services.BuildServiceProvider()"构建"所有服务，但.net core 3抱怨该方法会创建服务的其他副本，并建议我依赖注入服务作为配置"的参数. 我不知道该建议意味着什么，我想理解它.

I've just upgraded a .net core app from version 2.2 to 3. Inside the ConfigureServices method in startup.cs I need to resolve a service that is used by the authentication service. I was "building" all the services using "services.BuildServiceProvider()" but .net core 3 complains about the method creating additional copies of the services and suggesting me to dependency injecting services as parameters to 'configure'. I have no idea what the suggestion means and I'd like to understand it.

public virtual void ConfigureServices(IServiceCollection services)
{
    // Need to resolve this.
    services.AddSingleton<IManageJwtAuthentication, JwtAuthenticationManager>();

    var sp = services.BuildServiceProvider(); // COMPLAINING HERE!!
    var jwtAuthManager = sp.GetRequiredService<IManageJwtAuthentication>();

    services
        .AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
        .AddJwtBearer(c =>
        {
            c.TokenValidationParameters = new TokenValidationParameters
            {
                AudienceValidator = jwtAuthManager.AudienceValidator,
                // More code here...
            };
        }
}

答

但是.net核心3抱怨该方法会创建服务的其他副本，并建议我依赖注入服务作为配置"的参数.

but .net core 3 complains about the method creating additional copies of the services and suggesting me to dependency injecting services as parameters to 'configure'.

实际上，主机应自动调用ServiceCollection.BuildServiceProvider().您的代码services.BuildServiceProvider();将创建一个重复的服务提供商，该服务提供商默认为不同的，这可能会导致不一致的服务状态.请参阅引起的错误由多个服务提供商在这里.

Actually, the ServiceCollection.BuildServiceProvider() should be invoked by the Host automatically. Your code services.BuildServiceProvider(); will create a duplicated service provider that is different the default one, which might lead to inconsistent service states. See a bug caused by multiple Service Provider here.

要解决此问题，请

To solve this question, configure the options with dependency injection instead of creating a service provider and then locating a service.

对于您的代码，请按如下所示重写它们:

For your codes, rewrite them as below:

services.AddSingleton<IManageJwtAuthentication, JwtAuthenticationManager>();

services.AddOptions<JwtBearerOptions>(JwtBearerDefaults.AuthenticationScheme)
    .Configure<IManageJwtAuthentication>((opts,jwtAuthManager)=>{
        opts.TokenValidationParameters = new TokenValidationParameters
        {
            AudienceValidator = jwtAuthManager.AudienceValidator,
            // More code here...
        };
    });

services
    .AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
    .AddJwtBearer();

.net核心3依赖项注入服务作为“配置"的参数

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