net core 3 使用 autofac

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();
  }
}

public class Startup
{
  public Startup(IHostingEnvironment env)
  {
    // Do Startup-ish things like read configuration.
  }

  // This is the default if you don‘t have an environment specific method.
  public void ConfigureServices(IServiceCollection services)
  {
    // Add things to the service collection.
  }

  // This only gets called if your environment is Development. The
  // default ConfigureServices won‘t be automatically called if this
  // one is called.
  public void ConfigureDevelopmentServices(IServiceCollection services)
  {
    // Add things to the service collection that are only for the
    // development environment.
  }

  // This is the default if you don‘t have an environment specific method.
  public void ConfigureContainer(ContainerBuilder builder)
  {
    // Add things to the Autofac ContainerBuilder.
  }

  // This only gets called if your environment is Production. The
  // default ConfigureContainer won‘t be automatically called if this
  // one is called.
  public void ConfigureProductionContainer(ContainerBuilder builder)
  {
    // Add things to the ContainerBuilder that are only for the
    // production environment.
  }

  // This is the default if you don‘t have an environment specific method.
  public void Configure(IApplicationBuilder app, ILoggerFactory loggerFactory)
  {
    // Set up the application.
  }

  // This only gets called if your environment is Staging. The
  // default Configure won‘t be automatically called if this one is called.
  public void ConfigureStaging(IApplicationBuilder app, ILoggerFactory loggerFactory)
  {
    // Set up the application for staging.
  }
}