'ConfigureServices returning a System.IServiceProvider isn't supported.'

Question

I need ti use this AutoFac in ASP core 3.0

When I use this code in startu up:

public IServiceProvider ConfigureServices(IServiceCollection services) {     services.AddControllers();     return services.BuildAutofacServiceProvider(); } 

It show me this error:

'ConfigureServices returning an System.IServiceProvider isn't supported.'

And I change the program.cs by this:

public class Program {     public static void Main(string[] args)     {         CreateHostBuilder(args).Build().Run();     }      public static IHostBuilder CreateHostBuilder(string[] args) =>         Host.CreateDefaultBuilder(args)         .UseServiceProviderFactory(new AutofacServiceProviderFactory())             .ConfigureWebHostDefaults(webBuilder =>             {                 webBuilder.UseStartup<Startup>();             }); } 

But it not solved.

This is BuildAutofacServiceProvider() Code:

public static IServiceProvider BuildAutofacServiceProvider(this IServiceCollection services) {     var ContainerBuilder = new ContainerBuilder();     ContainerBuilder.Populate(services);     ContainerBuilder.AddService();     var container = ContainerBuilder.Build();      return new AutofacServiceProvider(container); } 

How can I solve this problem?

Answer 1

Startup syntax has changed for configuring Autofac for ASP.NET Core 3.0+

In addition to using the following on the host builder

.UseServiceProviderFactory(new AutofacServiceProviderFactory()) 

In Startup do the following format

public void ConfigureServices(IServiceCollection services) {     //... normal registration here      // Add services to the collection. Don't build or return     // any IServiceProvider or the ConfigureContainer method     // won't get called.      services.AddControllers(); }  // 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. If you // need a reference to the container, you need to use the // "Without ConfigureContainer" mechanism shown later. public void ConfigureContainer(ContainerBuilder builder) {     // Register your own things directly with Autofac     builder.AddMyCustomService();      //... } 

Reference Autofac documentation for ASP.NET Core 3.0+

Answer 2

Instead of Host in Program.cs you can use WebHost

public class Program {   public static void Main(string[] args)   {     CreateWebHostBuilder(args).Build().Run();   }    public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>     WebHost.CreateDefaultBuilder(args)       .UseStartup<Startup>(); } 

In this case following code works

public IServiceProvider ConfigureServices(IServiceCollection services) {   ...   var builder = new ContainerBuilder();    builder.Populate(services);   var container = builder.Build();   return new AutofacServiceProvider(container); }