在 Startup.cs 之外实施依赖注入

Question

我想在 ASP.NET 核心 1 中实施 依赖注入 。我知道 .Net Core 中的一切都是关于 DI 的。例如

   public void ConfigureServices(IServiceCollection services)
   {
      // Add application services.
     services.AddTransient<IDateTime, SystemDateTime>();
   }

但是对于拥有超过 20 个实体和服务的大项目，在 ConfigureServices 中编写所有这些代码行是非常困难和不可读的。我想知道这是否可能在 Startup.cs 之外实施依赖注入，然后将其添加到服务中。

感谢您的回答。

Answer 1

可以在Startup.cs

中编写IServiceCollection的扩展方法将大量服务注册封装到1行代码中

例如，这是我项目中的一个：

using cloudscribe.Core.Models;
using cloudscribe.Core.Models.Setup;
using cloudscribe.Core.Web;
using cloudscribe.Core.Web.Components;
using cloudscribe.Core.Web.Components.Editor;
using cloudscribe.Core.Web.Components.Messaging;
using cloudscribe.Core.Web.Navigation;
using cloudscribe.Web.Common.Razor;
using cloudscribe.Web.Navigation;
using cloudscribe.Web.Navigation.Caching;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc.Razor;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection.Extensions;
using Microsoft.Extensions.FileProviders;
using Microsoft.Extensions.Options;
using System.Reflection;
using Microsoft.AspNetCore.Authorization;

namespace Microsoft.Extensions.DependencyInjection
{
    public static class StartupExtensions
    {
        public static IServiceCollection AddCloudscribeCore(this IServiceCollection services, IConfigurationRoot configuration)
        {
            services.TryAddSingleton<IHttpContextAccessor, HttpContextAccessor>();
            services.Configure<MultiTenantOptions>(configuration.GetSection("MultiTenantOptions"));
            services.Configure<SiteConfigOptions>(configuration.GetSection("SiteConfigOptions"));
            services.Configure<UIOptions>(configuration.GetSection("UIOptions"));
            services.Configure<CkeditorOptions>(configuration.GetSection("CkeditorOptions"));
            services.Configure<CachingSiteResolverOptions>(configuration.GetSection("CachingSiteResolverOptions"));
            services.AddMultitenancy<SiteContext, CachingSiteResolver>();
            services.AddScoped<CacheHelper, CacheHelper>();
            services.AddScoped<SiteManager, SiteManager>();
            services.AddScoped<GeoDataManager, GeoDataManager>();
            services.AddScoped<SystemInfoManager, SystemInfoManager>();
            services.AddScoped<IpAddressTracker, IpAddressTracker>();
            services.AddScoped<SiteDataProtector>();
            services.AddCloudscribeCommmon();
            services.AddScoped<ITimeZoneIdResolver, RequestTimeZoneIdResolver>();
            services.AddCloudscribePagination();
            services.AddScoped<IVersionProviderFactory, VersionProviderFactory>();
            services.AddScoped<IVersionProvider, CloudscribeCoreVersionProvider>();
            services.AddTransient<ISiteMessageEmailSender, SiteEmailMessageSender>();
            services.AddTransient<ISmsSender, SiteSmsSender>();
            services.AddSingleton<IThemeListBuilder, SiteThemeListBuilder>();
            services.TryAddScoped<ViewRenderer, ViewRenderer>();
            services.AddSingleton<IOptions<NavigationOptions>, SiteNavigationOptionsResolver>();
            services.AddScoped<ITreeCacheKeyResolver, SiteNavigationCacheKeyResolver>();
            services.AddScoped<INodeUrlPrefixProvider, FolderTenantNodeUrlPrefixProvider>();
            services.AddCloudscribeNavigation(configuration);

            services.AddCloudscribeIdentity();

            return services;
        }


    }
}

在Startup.cs中我用一行代码调用了那个方法

services.AddCloudscribeCore(Configuration);

Answer 2

可以采用多种方法，但有些只是在 class 之间移动代码；我建议您考虑 Assembly Scanning，正如我在下面描述的第二个选项：

1. 'MOVE THE PROBLEM'：扩展方法

初始选项是使用 extension methods 来配置服务。

这是一个将多个服务注册包装到一个扩展方法中的示例：

    public static IServiceCollection AddCustomServices(this IServiceCollection services)
    {
        services.AddScoped<IBrowserConfigService, BrowserConfigService>();
        services.AddScoped<IManifestService, ManifestService>();
        services.AddScoped<IRobotsService, RobotsService>();
        services.AddScoped<ISitemapService, SitemapService>();
        services.AddScoped<ISitemapPingerService, SitemapPingerService>();

        // Add your own custom services here e.g.

        // Singleton - Only one instance is ever created and returned.
        services.AddSingleton<IExampleService, ExampleService>();

        // Scoped - A new instance is created and returned for each request/response cycle.
        services.AddScoped<IExampleService, ExampleService>();

        // Transient - A new instance is created and returned each time.
        services.AddTransient<IExampleService, ExampleService>();

        return services;
    }

可以在ConfigureServices内调用：

services.AddCustomServices();

注意： 这对于特定配置（例如，当服务需要向其传递多个选项时）作为 'builder pattern' 很有用，但是，没有解决必须手动编码注册多个服务的问题；这与编写相同的代码但在不同的 class 文件中本质上没有区别，并且仍然需要手动维护。

2。 'SOLVE THE PROBLEM'：装配扫描

'best practice'选项是Assembly Scanning，用于根据Implemented Interfaces自动查找和注册组件；下面是一个 Autofac 示例：

var assembly= Assembly.GetExecutingAssembly();

builder.RegisterAssemblyTypes(assembly)
       .Where(t => t.Name.EndsWith("Repository"))
       .AsImplementedInterfaces();

处理注册生命周期（或范围）的一个技巧是使用标记接口（空接口），例如 IScopedService，并使用它来扫描和注册具有适当生命周期的服务.这是注册多项服务的最低摩擦方法，它是自动的，因此 'zero maintenance'.

注意：内置ASP.Net核心DI实现不支持Assembly Scanning（如pf current，2016版本）；然而，Github（和 Nuget）上的 Scrutor 项目添加了此功能，它将服务和类型注册压缩为：

var collection = new ServiceCollection();

collection.Scan(scan => scan
    .FromAssemblyOf<ITransientService>()
        .AddClasses(classes => classes.AssignableTo<ITransientService>())
            .AsImplementedInterfaces()
            .WithTransientLifetime()
        .AddClasses(classes => classes.AssignableTo<IScopedService>())
            .As<IScopedService>()
            .WithScopedLifetime());

摘要:

Assembly Scanning 与 Extension Methods（如果适用）相结合将为您节省大量维护工作，并且在应用程序启动时执行一次，随后进行缓存。它避免了手动代码服务注册的需要。

Answer 3

可以写一个批量注册的扩展方法：

    public static void AddScopedFromAssembly(this IServiceCollection services, Assembly assembly)
    {
        var allServices = assembly.GetTypes().Where(p =>
            p.GetTypeInfo().IsClass &&
            !p.GetTypeInfo().IsAbstract);
        foreach (var type in allServices)
        {
            var allInterfaces = type.GetInterfaces();
            var mainInterfaces = allInterfaces.Except
                    (allInterfaces.SelectMany(t => t.GetInterfaces()));
            foreach (var itype in mainInterfaces)
            {
                services.AddScoped(itype, type); // if you want you can pass lifetime as a parameter
            }
        }
    }

和用法：

 services.AddScopedFromAssembly(assembly);

Answer 4

我最近（成功地）实现了程序集扫描方法，但最终发现 cluster_registrations_in_a_few_extension_methods 方法对于我自己和其他使用它的程序员来说更清晰。如果您将注册集群保持在注册类的定义位置附近，维护工作总是比注册类本身涉及的维护工作少得多。

Answer 5

将 DependenciesManager class 添加到您的项目并实施 AddApplicationRepositories 方法。

 public static class DependenciesManager
 {
        public static void AddApplicationRepositories(this IServiceCollection service)
        {
            var assembly = Assembly.GetExecutingAssembly();

            var services = assembly.GetTypes().Where(type =>
            type.GetTypeInfo().IsClass && type.Name.EndsWith("Repository") &&
            !type.GetTypeInfo().IsAbstract);
      
            foreach (var serviceType in services)
            {
                var allInterfaces = serviceType.GetInterfaces();
                var mainInterfaces = allInterfaces.Except
                (allInterfaces.SelectMany(t => t.GetInterfaces()));

                foreach (var iServiceType in mainInterfaces)
                {
                    service.AddScoped(iServiceType, serviceType);
                }
            }
        }
   }

在Startupclass中添加services.AddApplicationRepositories();在ConfigureServices方法中。

public void ConfigureServices(IServiceCollection services)
{
     services.AddApplicationRepositories();
}

如果您需要注册不同的服务，只需实现DependenciesManager class中的更多方法即可。比如需要注册一些Authorization Handler服务，实现AddAuthorizationHandlers方法即可：

 public static void AddAuthorizationHandlers(this IServiceCollection service)
  {
        var assembly = Assembly.GetExecutingAssembly();

        var services = assembly.GetTypes().Where(type =>
            type.GetTypeInfo().IsClass && type.Name.EndsWith("Handler") &&
            !type.GetTypeInfo().IsAbstract);

        foreach (var serviceType in services)
        {
            var allInterfaces = serviceType.GetInterfaces();
            var mainInterfaces = allInterfaces.Except
                (allInterfaces.SelectMany(t => t.GetInterfaces()));

            foreach (var iServiceType in mainInterfaces)
            {
                service.AddScoped(iServiceType, serviceType);
            }
        }
    }

并在 Startup class 中添加：

 services.AddAuthorizationHandlers();

Notes: the names of the services and its implementation you want to register must end with "Repository" or "Handler" according to my answer.

在 Startup.cs 之外实施依赖注入

Implement dependency injection outside of Startup.cs

c#

dependency-injection

.net-core

asp.net-core