.NET Core Scoped通过DI在Singleton中调用

无法解析范围内的服务Microsoft.AspNetCore.Mvc根提供商提供的.ViewFeatures.Internal.IViewBufferScope 解决方案 在Core 1.1中，没有检查嵌套在Singleton中的Scoped.实际上是.但是默认情况下未启用它.这是IMO在.NET Core 1中的错误.我的Singleton服务内部的上下文工作正常.这种方法非常有用，这就是为什么默认情况下阻止它是一件好事.例如，DbContext不是线程安全的，并且在应用程序运行期间将其保持活动状态几乎会导致并发错误，这些并发错误仅在生产环境中运行时同时出现多个请求时才会出现.这不会导致您遇到的问题，这是例外，而不是常规.无法从根提供者解析作用域服务'ArithmosDaily.IHangfireJobSchedulerService'.我仍然不知道那甚至意味着什么.该错误确实非常令人困惑.这意味着，对于.NET Core容器，您应该始终从 IServiceScope.ServiceProvider (或注入的 IServiceProvider)进行解析，而不是从根源 IServiceProvider .在ASP.NET Core请求中运行时，框架将代表您自动调用 ServiceProviderServiceExtensions.CreateScope`，并使用该范围为您解析控制器和其他服务.在网络请求之外运行时，您可能需要自己创建一个范围.I'm getting an error in 2.0 that I used not to get in .Net Core 1.1.Cannot consume scoped service 'ArithmosDaily.Data.ArithmosContext' from singleton 'ArithmosDaily.IHangfireJobSchedulerService'.I am using Hangfire, and I need it to access my database (so I inject my context through DI) to update the database with some data from an API on a schedule. So it appears the DbContext is instantiated as Scoped, and I am setting my Hangfire service as a Singleton. In Core 1.1, there was no check for Scoped nested inside a Singleton. I know this concept works, because I ripped it out of another of my projects in a Core 1.1 project and nesting the Context inside my Singleton service works fine. (Which is annoying me that Microsoft feels the need to control me just because I may do something bad).So, I change my Hangfire Service from Singleton to Scoped, hoping since my DbContext is apparently Scoped, that Scoped inside Scoped would be fine and instead I get this error: Cannot resolve scoped service 'ArithmosDaily.IHangfireJobSchedulerService' from root provider. I still have no clue what that one even means.After doing a little bit of digging, I came across the two links at the bottom of my post (and so far that's all I can find). I tried setting services.BuildServiceProvider(false); in my Startup as suggested in the first link, but that didn't change anything in my Configure: I still get the error when setting up my service.I am totally stumped and not sure what else to try. Maybe I have code in the wrong spot? I'm not sure.Here is my code for Startup and Configure:public void ConfigureServices(IServiceCollection services){ services.BuildServiceProvider(false); string conn = Configuration.GetConnectionString("Arithmos"); services.AddDbContext<ArithmosContext>(options => options.UseSqlite(conn)); services.AddMvc(); services.AddHangfire(x => x.UseSQLiteStorage(conn)); services.AddScoped<IHangfireJobSchedulerService, HangfireJobSchedulerService>();}public void Configure(IApplicationBuilder app, IHostingEnvironment env, IApplicationLifetime lifetime){ lifetime.ApplicationStarted.Register(OnStartup); lifetime.ApplicationStopping.Register(OnShutdown); if (env.IsDevelopment()) { app.UseDeveloperExceptionPage(); app.UseBrowserLink(); } else app.UseExceptionHandler("/Error"); app.UseStaticFiles(); app.UseMvc(routes => { routes.MapRoute( name: "default", template: "{controller}/{action=Index}/{id?}"); }); app.UseHangfireServer(); app.UseHangfireDashboard(options: new DashboardOptions { Authorization = new[] { new HangfireAuthorizationFilter() } }); jobSchedulerService = app.ApplicationServices.GetRequiredService<IHangfireJobSchedulerService>();}I have come across these questions but they haven't helped me too much:ASP.Net Core 2 ServiceProviderOptions.ValidateScopes PropertyCannot resolve scoped service Microsoft.AspNetCore.Mvc.ViewFeatures.Internal.IViewBufferScope from root provider 解决方案 In Core 1.1, there was no check for Scoped nested inside a Singleton.There was, actually. But it was not enabled by default. This was IMO a mistake in .NET Core 1. the Context inside my Singleton service works fine.That such thing works is rather exceptional, and that's why blocking this by default is a good thing. A DbContext, for instance, is not thread-safe and keeping it alive for the duration of the application will in almost all cases lead to concurrency bugs that will only appear when running in production, when multiple requests come in simultaneously.It this doesn't cause bugs in your situation, it is the exception, not the rule. Cannot resolve scoped service 'ArithmosDaily.IHangfireJobSchedulerService' from root provider. I still have no clue what that one even means.That error is indeed very confusing. What this means is that, with the .NET Core container, you should always resolve from an IServiceScope.ServiceProvider (or an injected IServiceProvider), but never from the rootIServiceProvider. When running inside an ASP.NET Core request, the framework will automatically callServiceProviderServiceExtensions.CreateScope` on your behalf and use that scope to resolve controllers and other services for you. When running outside a web request, you might need to create a scope yourself. 这篇关于.NET Core Scoped通过DI在Singleton中调用的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 上岸，阿里云！