ASP.NET Core 2 問題中的依賴注入

Question

更新

我將啟動更改為：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Actio.Api.Handlers;
using Actio.Api.Repositories;
using Actio.Common.Auth;
using Actio.Common.Events;
using Actio.Common.Mongo;
using Actio.Common.RabbitMq;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace Actio.Api
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc();
            services.AddJwt(Configuration);
            services.AddRabbitMq(Configuration);
            services.AddMongoDB(Configuration);
            services.AddScoped<IEventHandler<ActivityCreated>, ActivityCreatedHandler>();
            services.AddScoped<IActivityRepository, ActivityRepository>();

        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            // app.ApplicationServices.GetService<IDatabaseInitializer>().InitializeAsync();

            using (var serviceScope = app.ApplicationServices.CreateScope())
            {
                serviceScope.ServiceProvider.GetService<IDatabaseInitializer>().InitializeAsync();
            }
            app.UseAuthentication();
            app.UseMvc();
        }
    }
}

但是現在我在SubscribeToEvent 中遇到錯誤：無法解析范圍服務

'Actio.Common.Events.IEventHandler`1[Actio.Common.Events.ActivityCreated]' from root provider.' 

在我的 ServiceHost.cs 中。

服務主機

using System;
using Actio.Common.Commands;
using Actio.Common.Events;
using Actio.Common.RabbitMq;
using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using RawRabbit;

namespace Actio.Common.Services
{
    public class ServiceHost : IServiceHost
    {
        private readonly IWebHost _webHost;

        public ServiceHost(IWebHost webHost)
        {
            _webHost = webHost;
        }

        public void Run() => _webHost.Run();

        public static HostBuilder Create<TStartup>(string[] args) where TStartup : class
        {
            Console.Title = typeof(TStartup).Namespace;
            var config = new ConfigurationBuilder()
                .AddEnvironmentVariables()
                .AddCommandLine(args)
                .Build();
            var webHostBuilder = WebHost.CreateDefaultBuilder(args)
                .UseConfiguration(config)
                .UseStartup<TStartup>();

            return new HostBuilder(webHostBuilder.Build());
        }

        public abstract class BuilderBase 
        {
            public abstract ServiceHost Build();
        }

        public class HostBuilder : BuilderBase
        {
            private readonly IWebHost _webHost;
            private IBusClient _bus;

            public HostBuilder(IWebHost webHost)
            {
                _webHost = webHost;
            }

            public BusBuilder UseRabbitMq()
            {
                _bus = (IBusClient)_webHost.Services.GetService(typeof(IBusClient));

                return new BusBuilder(_webHost, _bus);
            }

            public override ServiceHost Build()
            {
                return new ServiceHost(_webHost);
            }
        }

        public class BusBuilder : BuilderBase
        {
            private readonly IWebHost _webHost;
            private IBusClient _bus; 

            public BusBuilder(IWebHost webHost, IBusClient bus)
            {
                _webHost = webHost;
                _bus = bus;
            }

            public BusBuilder SubscribeToCommand<TCommand>() where TCommand : ICommand
            {
                var handler = (ICommandHandler<TCommand>)_webHost.Services
                    .GetService(typeof(ICommandHandler<TCommand>));
                _bus.WithCommandHandlerAsync(handler);

                return this;
            }

            public BusBuilder SubscribeToEvent<TEvent>() where TEvent : IEvent
            {
                var handler = (IEventHandler<TEvent>)_webHost.Services
                    .GetService(typeof(IEventHandler<TEvent>));
                _bus.WithEventHandlerAsync(handler);

                return this;
            }

            public override ServiceHost Build()
            {
                return new ServiceHost(_webHost);
            }
        }
    }
}

-------------------------------------------------- -----------------------------

我最近開始用 RabbitMQ 學習微服務。 經過一番努力，我得到了一個代碼示例，但我無法運行它，因為它給出了錯誤:"System.InvalidOperationException: 'Cannot resolve scoped service 'Actio.Common.Mongo.IDatabaseInitializer' from root provider.'"

我想了解這段代碼，以便更好地理解微服務。

代碼啟動.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Actio.Api.Handlers;
using Actio.Api.Repositories;
using Actio.Common.Auth;
using Actio.Common.Events;
using Actio.Common.Mongo;
using Actio.Common.RabbitMq;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace Actio.Api
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc();
            services.AddJwt(Configuration);
            services.AddRabbitMq(Configuration);
            services.AddMongoDB(Configuration);
            services.AddScoped<IEventHandler<ActivityCreated>, ActivityCreatedHandler>();
            services.AddScoped<IActivityRepository, ActivityRepository>();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
          //Giving Error in below line


app.ApplicationServices.GetService<IDatabaseInitializer>().InitializeAsync();
                app.UseAuthentication();
                app.UseMvc();
            }
        }
    }

有人可以幫忙，以便我可以調試並更好地理解。

謝謝

Answer 1

以下錯誤試圖告訴您您正在將IDatabaseInitializer注冊為范圍服務，但試圖在范圍之外訪問它：

"System.InvalidOperationException: 'Cannot resolve scoped service 'Actio.Common.Mongo.IDatabaseInitializer' from root provider.'"

嘗試創建一個范圍，然后使用如下服務：

using (var serviceScope = app.ApplicationServices.CreateScope())
{
    serviceScope.ServiceProvider.GetService<IDatabaseInitializer>().InitializeAsync();
}

Answer 2

解決方案是禁用范圍驗證。

因此，在文件 src\\actio.common\\services\\servicehost.cs 的第 31-32 行之間添加以下內容：

.UseDefaultServiceProvider(options => options.ValidateScopes = false)

要解決這個問題，從另一個變化替代方法services.AddScoped到services.AddSingleton在Program.cs中，用一個單獨的工作是要避免所有范圍的審定及。