使用autofac时会遇到此错误：：'不支持配置服务返回System.IServiceProvider。'

Question

我要在我的项目中使用autofac。

我写这家创业公司：

  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 IServiceProvider ConfigureServices(IServiceCollection services)
    {
        services.AddControllers();
        var builder = new ContainerBuilder();
        builder.RegisterAssemblyTypes(Assembly.GetEntryAssembly())
                .AsImplementedInterfaces();
        builder.Populate(services);
        builder.AddDispatchers();

        var conteiner = builder.Build();

        return new AutofacServiceProvider(conteiner);
    }

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

        app.UseHttpsRedirection();

        app.UseRouting();

        app.UseAuthorization();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });
    }
}

这不是我的program.cs：

public class Program
{
    public static void Main(string[] args)
    {
        var host = Host.CreateDefaultBuilder(args)
     .UseServiceProviderFactory(new AutofacServiceProviderFactory())
     .ConfigureWebHostDefaults(webHostBuilder =>
     {
         webHostBuilder
          .UseContentRoot(Directory.GetCurrentDirectory())
          .UseIISIntegration()
          .UseStartup<Startup>();
     })
     .Build();

        host.Run();
    }
}

但是它告诉我这个错误：

'不支持ConfigureServices返回System.IServiceProvider。'

如何解决此问题？

Answer 1

这是因为您正在尝试3.0之前的版本。 Check the ConfigureServices docs。它不支持IServiceProvider返回类型。

public virtual void ConfigureServices (Microsoft.Extensions.DependencyInjection.IServiceCollection services);

从autofac文档：

这不适用于ASP.NET Core 3+或.NET Core 3+通用托管支持-ASP.NET Core 3已弃用从ConfigureServices返回服务提供者的功能

检查Autofac net core guide发布3.0

public class Program
{
  public static void Main(string[] args)
  {
    // ASP.NET Core 3.0+:
    // The UseServiceProviderFactory call attaches the
    // Autofac provider to the generic hosting mechanism.
    var host = Host.CreateDefaultBuilder(args)
        .UseServiceProviderFactory(new AutofacServiceProviderFactory())
        .ConfigureWebHostDefaults(webHostBuilder => {
          webHostBuilder
            .UseContentRoot(Directory.GetCurrentDirectory())
            .UseIISIntegration()
            .UseStartup<Startup>();
        })
        .Build();

    host.Run();
  }
}

public class Startup
{
  public Startup(IHostingEnvironment env)
  {
    // In ASP.NET Core 3.0 `env` will be an IWebHostingEnvironment, not IHostingEnvironment.
    var builder = new ConfigurationBuilder()
        .SetBasePath(env.ContentRootPath)
        .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
        .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
        .AddEnvironmentVariables();
    this.Configuration = builder.Build();
  }

  public IConfigurationRoot Configuration { get; private set; }

  public ILifetimeScope AutofacContainer { get; private set; }

  // ConfigureServices is where you register dependencies. This gets
  // called by the runtime before the ConfigureContainer method, below.
  public void ConfigureServices(IServiceCollection services)
  {
    // Add services to the collection. Don't build or return
    // any IServiceProvider or the ConfigureContainer method
    // won't get called.
    services.AddOptions();
  }

  // ConfigureContainer is where you can register things directly
  // with Autofac. This runs after ConfigureServices so the things
  // here will override registrations made in ConfigureServices.
  // Don't build the container; that gets done for you by the factory.
  public void ConfigureContainer(ContainerBuilder builder)
  {
    // Register your own things directly with Autofac, like:
    builder.RegisterModule(new MyApplicationModule());
  }

  // Configure is where you add middleware. This is called after
  // ConfigureContainer. You can use IApplicationBuilder.ApplicationServices
  // here if you need to resolve things from the container.
  public void Configure(
    IApplicationBuilder app,
    ILoggerFactory loggerFactory)
  {
    // If, for some reason, you need a reference to the built container, you
    // can use the convenience extension method GetAutofacRoot.
    this.AutofacContainer = app.ApplicationServices.GetAutofacRoot();

    loggerFactory.AddConsole(this.Configuration.GetSection("Logging"));
    loggerFactory.AddDebug();
    app.UseMvc();
  }
}