Proposal: Support IServiceProviderFactory

[davidfowl]

Based on aspnet/DependencyInjection#442

The WebHostBuilder API would take advantage of this by using it as a way to override the default IServiceProvider implementation without returning it directly from the application's Startup class. The wire up could look like this:

public static void Main(string[] args)
{
    var host = new WebHostBuilder()
        .UseKestrel()
        .UseAutofac() // Replace the built-in IServiceProviderFactory with an autofac impl
        .UseContentRoot(Directory.GetCurrentDirectory())
        .UseStartup<Startup>()
        .Build();

    host.Run();
}

One downside to this is that you don't get direct access to the container APIs in the Startup class (which is part of the benefit besides being able to swap out the default impl).

In the above example, UseAutofac would wire up the IServiceProviderFactory. We could also extend the ConventionBasedStartup to allow authoring a ConfigureContainer method that takes the concrete ContainerBuilder directly:

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

    public void ConfigureContainer(ContainerBuilder builder)
    {
        builder.RegisterInstance(new TaskRepository())
           .As<ITaskRepository>();
    }

    public void Configure(IApplicationBuilder app)
    {
        app.UseMvc();
    }
}

[guardrex]

you don't get direct access to the container APIs in the Startup class

Will there be any consequences for those who despise the vile and dreaded Startup class? 😄

public static void Main(string[] args)
{
    var host = new WebHostBuilder()
        .UseKestrel()
        .UseContentRoot(Directory.GetCurrentDirectory())
        .ConfigureServices(services =>
        {
            ...
        })
        .Configure((app) =>
        {
            ...
        })
        .Build();

    host.Run();
}

[davidfowl]

You can't replace the IServiceProvider today if you configure everything with the WebHostBuilder today. See #550

[guardrex]

Fair enough ... just checking. Since I don't (with this pattern "can't" really), it won't affect me. 😄

[Tratcher]

How does it work if UseKestrel is already adding and accessing services?

[davidfowl]

@Tratcher what specifically are you asking about? Passing the IServiceProvider directly or the new IServiceProviderFactory proposal?

[Tratcher]

In the new IServiceProviderFactory.

[davidfowl]

Works fine. Just like it does today. UseKestrel wires up an IConfigureOptions<KestrelOptions> that captures the IServicerProvider provided by the application.