c# - 使用 Autofac 4 和 vNext 自注册库

Question

我想为我的 ASP.Net 5.0/MVC 6 应用程序创建一个插件环境。我使用 Autofac 作为 IOC 容器，我喜欢从 DNX LibraryManager 中的构建加载插件(类库)。使用库管理器的目的是，我不必关心 NuGet 包和框架。

我遇到的问题是生命周期，我必须在 LibraryManager 实例可用之前构建 IOC 容器。因为 Autofac 容器提供了他自己的 IServiceProvider 实例，我必须在 ConfigureService() 方法调用 (AddAutofac) 中注入(inject)它。

有人知道如何让它工作吗？

更新:我已经在 David 的帮助下解决了我的问题，并更新了代码以使其适用于候选发布版本。我还添加了对配置的支持。

在我的 DNX 类库中，我实现了一个自注册类:

public class AutofacModule : Module
{
    protected override void Load(ContainerBuilder builder)
    {
        builder.Register(c => new SimpleService())
               .As<IService>()
               .InstancePerLifetimeScope();
    }
}

在我的 MVC WebApplication 中，我添加了类库作为依赖项。

启动.cs

public IConfiguration Configuration { get; set; }

public class Startup
{
    public Startup( IApplicationEnvironment applicationEnvironment )
    {
        IConfigurationBuilder configurationBuilder = new ConfigurationBuilder();
        configurationBuilder.SetBasePath( applicationEnvironment.ApplicationBasePath );

        configurationBuilder.AddJsonFile( "appsettings.json" );
        configurationBuilder.AddJsonFile( "autofac.json" );
        configurationBuilder.AddEnvironmentVariables();

        this.Configuration = configurationBuilder.Build();
    }

    public void ConfigureServices(IServiceCollection services)
    {                       
        services.AddMvc();                                     
        services.AddDependencies();    
    }

    public void Configure(IApplicationBuilder applicationBuilder, IHostingEnvironment hostingEnvironment)
    { 
        applicationBuilder.UseDependencies( this.Configuration );
        applicationBuilder.UseStaticFiles();      
        applicationBuilder.UseMvc();
    }
}     

我创建了一个 DependencyResolver 来保留 ContainerBuilder 实例。

依赖解析器.cs

public class DependencyResolver : IDependencyResolver
{
    private IContainer container;
    private readonly ContainerBuilder builder;     

    public DependencyResolver()
    {
        this.builder = new ContainerBuilder();   
    }

    public void RegisterModule( IModule module )
    {
        this.builder.RegisterModule( module );
    }

    public void RegisterModules( IEnumerable<Assembly> assemblies )
    {         
        this.builder.RegisterAssemblyModules(assemblies.ToArray());  
    }       

    public void Populate( IServiceCollection services)
    {
        this.builder.Populate( services );
    }

    public void Build()
    {
        this.container = this.builder.Build();
    }

    public T Resolve<T>() where T : class
    {                                                 
        return this.container?.Resolve<T>();              
    }      
}

IDependencyResolver.cs

public interface IDependencyResolver
{
    void RegisterModule( IModule module );
    void RegisterModules( IEnumerable<Assembly> assemblies );   
    void Populate(IServiceCollection services);
    void Build();
    T Resolve<T>() where T : class;
}

最后但同样重要的是我创建了一个扩展类

DependencyResolverExtensions.cs

public static class DependencyResolverExtensions
{
    public static IServiceCollection AddDependencies( this IServiceCollection services )
    {
        DependencyResolver dependencyResolver = new DependencyResolver();
        dependencyResolver.Populate(services);

        ServiceDescriptor serviceDescriptor = new ServiceDescriptor(typeof ( IDependencyResolver ), dependencyResolver );
        services.TryAdd(serviceDescriptor);

        return services;
    }

    public static IApplicationBuilder UseDependencies(this IApplicationBuilder applicationBuilder, IConfiguration configuration)
    {
        IDependencyResolver dependencyResolver = applicationBuilder.GetService<IDependencyResolver>();
        if (dependencyResolver == null) return applicationBuilder;

        ILibraryManager libraryManager = applicationBuilder.GetService<ILibraryManager>();
        if (libraryManager == null) return applicationBuilder;

        IEnumerable<Assembly> assemblies = libraryManager.GetLoadableAssemblies();
        dependencyResolver.RegisterModules(assemblies);

        ConfigurationModule configurationModule = new ConfigurationModule( configuration );
        dependencyResolver.RegisterModule( configurationModule );

        dependencyResolver.Build();        

        IServiceProvider serviceProvider = dependencyResolver.Resolve<IServiceProvider>();
        applicationBuilder.ApplicationServices = serviceProvider;

        return applicationBuilder;
    }

    public static IEnumerable<Assembly> GetLoadableAssemblies(this ILibraryManager libraryManager)
    {
        List<Assembly> result = new List<Assembly>();    

        IEnumerable<Library> libraries = libraryManager.GetLibraries();    

        IEnumerable<AssemblyName> assemblyNames = libraries.SelectMany(e => e.Assemblies).Distinct();
        assemblyNames = Enumerable.Where(assemblyNames, e => e.Name.StartsWith("MyLib."));

        foreach (AssemblyName assemblyName in assemblyNames)
        {
            Assembly assembly = Assembly.Load(assemblyName);
            result.Add(assembly);
        }

        return result;
    }

    public static T GetService<T>(this IApplicationBuilder applicationBuilder) where T : class
    {
        return applicationBuilder.ApplicationServices.GetService(typeof (T)) as T;
    }
}

如果您需要在不同的实现之间切换，例如模拟数据和真实数据，您可以使用 Autofac 配置。

autofac.json

{
    "components": [
        {
            "type": "MyLib.Data.EF.EntitiesData, MyLib.Data.EF",
            "services": [
                {
                    "type": "MyLib.Abstractions.IDataRepository, MyLib.Abstractions"
                }
            ]
        }
    ]
}

Answer 1

遗憾的是 ConfigureServices 是不可注入(inject)的，这会使这变得容易得多。

查看代码，您应该安全地替换 Configure(...) 中的 IServiceProvider 而不是 ConfigureServices(...) 并获得预期的行为。 ApplicationServices is setable .

在您的 UseAutofac 方法中，您应该能够执行如下操作:

public static IApplicationBuilder UseAutofac( [NotNull] this IApplicationBuilder applicationBuilder )
{
    IAutofacResolver autofacResolver = applicationBuilder.GetService<IAutofacResolver>();
    ILibraryManager libraryManager = applicationBuilder.GetService<ILibraryManager>();

    autofacResolver.RegisterLibraryModules( libraryManager);
    applicationBuilder.ApplicationServices = autofacResolver.Resolve();

    return applicationBuilder;
}