Swashbuckle.aspnetcore: Exception on run: No service for type 'Microsoft.AspNetCore.Mvc.ApiExplorer.IApiDescriptionGroupCollectionProvider' has been registered.

[oscarwest]

I can't seem to get swashbuckle to work for my .net core project.
"Swashbuckle.AspNetCore": "1.0.0-rc1"

I have had success with NSwag middleware but would like to get this working. Eventually adding in Auth0/OAuth2 support with AD for the swagger docs.
https://github.com/NSwag/NSwag

Some possible info from project.json

"dependencies": {
    "Microsoft.NETCore.App": {
      "version": "1.1.0",
      "type": "platform"
    },

  "frameworks": {
    "netcoreapp1.0": {
      "dependencies": {
        "Microsoft.NETCore.App": {
          "version": "1.1.0",
          "type": "platform"
        },
    "imports": [
        "dotnet5.6",
        "portable-net45+win8"
      ]
    }

Some possible relevant info from startup.cs, in order

services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1", new Info { Title = "My API", Version = "v1" });
            });

app.UseSwagger();
            app.UseSwaggerUi(c =>
            {
                c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
            });
app.UseMvcWithDefaultRoute();

Throws the following exception when you try dotnet run:

Unhandled Exception: System.InvalidOperationException: No service for type 'Microsoft.AspNetCore.Mvc.ApiExplorer.IApiDescriptionGroupCollectionProvider' has been registered.
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider)
   at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenOptions.CreateSwaggerProvider(IServiceProvider serviceProvider)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitTransient(TransientCallSite transientCallSite, ServiceProvider provider)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.<>c__DisplayClass16_0.<RealizeService>b__0(ServiceProvider provider)
   at Microsoft.Extensions.Internal.ActivatorUtilities.ConstructorMatcher.CreateInstance(IServiceProvider provider)
   at Microsoft.Extensions.Internal.ActivatorUtilities.CreateInstance(IServiceProvider provider, Type instanceType, Object[] parameters)
   at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.<>c__DisplayClass3_0.<UseMiddleware>b__0(RequestDelegate next)
   at Microsoft.AspNetCore.Builder.Internal.ApplicationBuilder.Build()
   at Microsoft.AspNetCore.Hosting.Internal.WebHost.BuildApplication()
   at Microsoft.AspNetCore.Hosting.WebHostBuilder.Build()
   at *.API.Program.Main(String[] args) in /Users/west/projects/*-backend-core/*.API/Program.cs:line 24

Program.cs

public class Program
    {
        private static readonly Dictionary<string, string> defaults = new Dictionary<string, string> {
            { WebHostDefaults.EnvironmentKey, "development" }
        };

        public static void Main(string[] args)
        {
            // Let environment variable be set from cli
            var config = new ConfigurationBuilder()
                .AddInMemoryCollection(defaults)
                .AddEnvironmentVariables("ASPNETCORE_")
                .AddCommandLine(args)
                .Build();

            var host = new WebHostBuilder()
            .UseConfiguration(config)
            .UseKestrel()
            .UseAzureAppServices()
            .UseContentRoot(Directory.GetCurrentDirectory())
            .UseUrls("http://localhost:5001")
            .UseStartup<Startup>()
            .Build();

            host.Run();
        }
    }

[domaindrivendev]

In your _Startup.cs_, does the _ConfigureServices_ method contain the following line:

services.AddMvc();

Swashbuckle depends on one of the services (the one mentioned in the exception message you provided) that's registered with the Mvc stack.

[oscarwest]

We are using:

services.AddMvcCore()
                .AddJsonFormatters(jsonOptions => {
                    jsonOptions.DateTimeZoneHandling = DateTimeZoneHandling.Utc;
                })
                .AddAuthorization(options => {
stuff               });

[domaindrivendev]

Any particular reason why you're using _AddMvcCore_ instead of _AddMvc_?

As the name implies, the former adds the bare bones MVC stack where as the latter adds the stack plus some additional services. One of the additional services is _ApiExplorer_, the built-in metadata layer that SB relies on. You can either switch to _AddMvc_ or you can use _AddMvcCore_ and then explicitly add the _ApiExplorer_ service:

services.AddMvcCore()
    .AddApiExplorer();

To be honest, I wasn't even aware of the _AddMvcCore_ option. I'll try get something into the docs as I'm sure others will encounter this. Let me know if this resolves your issue?

[domaindrivendev]

See https://github.com/domaindrivendev/Swashbuckle.AspNetCore#swashbuckle--apiexplorer

[oscarwest]

Adding the following line made everything work, thank you!

services.AddMvcCore()
    .AddApiExplorer();