UseStartup on GenericWebHostBuilder should fail when Startup.ConfigureServices returns an IServiceProvider

Right now it’s being ignored and it should throw instead.

Program.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

namespace WebApplication44
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateWebHostBuilder(args).Build().Run();
        }

        public static IHostBuilder CreateWebHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(builder =>
                {
                    builder.UseStartup<Startup>();
                });
    }
}

Startup.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;

namespace WebApplication44
{
    public class Startup
    {
        // This method gets called by the runtime. Use this method to add services to the container.
        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
        public IServiceProvider ConfigureServices(IServiceCollection services)
        {
            return services.BuildServiceProvider();
        }

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

            app.Run(async (context) =>
            {
                await context.Response.WriteAsync("Hello World!");
            });
        }
    }
}

Here’s the code that supposed to do that check.

https://github.com/aspnet/AspNetCore/blob/cc899e2be729364589ba7f4392bce9942e4faca4/src/Hosting/Hosting/src/GenericHost/GenericWebHostBuilder.cs#L245-L249

[davidfowl]

@HassanHashemi Returning an IServiceProvider from Startup.ConfigureServices does not compose with other calls to ConfigureServices. That pattern is the reason it was so difficult to implement allowing test services to override services added in Startup. It’s also the reason why ConfigureContainer only works if you don’t directly return the IServiceProvider from the ConfigureSevices.

[Tratcher]

Comments on closed issues are not tracked, please open a new issue with the details for your scenario.