Swagger Generator (msbuild) fails on full .NET Framework with Microsoft.AspNetCore.Mvc 2.2

The failing combination is exactly net462 + Microsoft.AspNetCore.Mvc 2.2.0. Works fine with netcoreapp2.2 + Microsoft.AspNetCore.Mvc 2.2.0 and net462 + Microsoft.AspNetCore.Mvc 2.1.3.

Repro & Build

Installed packages:

• Microsoft.AspNetCore.Mvc 2.2.0
• NSwag.AspNetCore 12.1.0
• NSwag.MSBuild 12.1.0

Invoking after build target

$(NSwagExe) aspnetcore2swagger "/assembly:$(TargetPath)" "/output:$(OutputPath)swagger.json"

The command fails with the following exception:

NSwag command line tool for .NET 4.6.1+ WinX64, toolchain v12.1.0.0 (NJsonSchema v9.13.28.0 (Newtonsoft.Json v11.0.0.0))
  Visit http://NSwag.org for more information.
  NSwag bin directory: C:\Users\appveyor\.nuget\packages\nswag.msbuild\12.1.0\tools\Win
  System.InvalidOperationException: The ConfigureServices method must either be parameterless or take only one parameter of type IServiceCollection.
  
  Server stack trace: 
     at Microsoft.AspNetCore.Hosting.Internal.ConfigureServicesBuilder.InvokeCore(Object instance, IServiceCollection services)
     at Microsoft.AspNetCore.Hosting.Internal.StartupLoader.ConfigureServicesDelegateBuilder`1.<>c__DisplayClass14_0.<ConfigureServices>g__ConfigureServicesWithContainerConfiguration|0(IServiceCollection services)
     at Microsoft.AspNetCore.Hosting.ConventionBasedStartup.ConfigureServices(IServiceCollection services)
     at Microsoft.AspNetCore.Hosting.Internal.WebHost.EnsureApplicationServices()
     at Microsoft.AspNetCore.Hosting.Internal.WebHost.Initialize()
     at Microsoft.AspNetCore.Hosting.WebHostBuilder.Build()
     at NSwag.Commands.SwaggerGeneration.SwaggerGeneratorCommandBase`1.<CreateWebHostAsync>d__110.MoveNext()
  --- End of stack trace from previous location where exception was thrown ---
     at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
     at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
     at NSwag.Commands.SwaggerGeneration.AspNetCore.AspNetCoreToSwaggerCommand.<RunIsolatedAsync>d__44.MoveNext()
  --- End of stack trace from previous location where exception was thrown ---
     at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
     at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
     at NSwag.Commands.IsolatedCommandBase`1.IsolatedCommandAssemblyLoader`1.Run(String commandType, String commandData, String[] assemblyPaths, String[] referencePaths)
     at System.Runtime.Remoting.Messaging.StackBuilderSink._PrivateProcessMessage(IntPtr md, Object[] args, Object server, Object[]& outArgs)
     at System.Runtime.Remoting.Messaging.StackBuilderSink.SyncProcessMessage(IMessage msg)
  
  Exception rethrown at [0]: 
     at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
     at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
     at NSwag.Commands.IsolatedCommandBase`1.IsolatedCommandAssemblyLoader`1.Run(String commandType, String commandData, String[] assemblyPaths, String[] referencePaths)
     at NSwag.Commands.IsolatedCommandBase`1.<>c__DisplayClass17_0.<RunIsolatedAsync>b__0()
     at System.Threading.Tasks.Task`1.InnerInvoke()
     at System.Threading.Tasks.Task.Execute()
  --- End of stack trace from previous location where exception was thrown ---
     at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
     at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
     at NSwag.Commands.IsolatedCommandBase`1.<RunIsolatedAsync>d__17.MoveNext()
  --- End of stack trace from previous location where exception was thrown ---
     at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
     at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
     at NSwag.Commands.IsolatedSwaggerOutputCommandBase`1.<RunAsync>d__9.MoveNext()
  --- End of stack trace from previous location where exception was thrown ---
     at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
     at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
     at NSwag.Commands.SwaggerGeneration.AspNetCore.AspNetCoreToSwaggerCommand.<RunAsync>d__39.MoveNext()
  --- End of stack trace from previous location where exception was thrown ---
     at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
     at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
     at NConsole.CommandLineProcessor.<ProcessSingleAsync>d__12.MoveNext()
  --- End of stack trace from previous location where exception was thrown ---
     at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
     at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
     at NConsole.CommandLineProcessor.<ProcessAsync>d__11.MoveNext()
  --- End of stack trace from previous location where exception was thrown ---
     at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
     at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
     at NConsole.CommandLineProcessor.Process(String[] args, Object input)
     at NSwag.Commands.NSwagCommandProcessor.Process(String[] args)
C:\projects\nswag-issue-mvc22\net462-mvc21\nswag.targets(7,9): error MSB3073: The command ""C:\Users\appveyor\.nuget\packages\nswag.msbuild\12.1.0\build\../tools/Win/NSwag.exe" aspnetcore2swagger "/assembly:C:\projects\nswag-issue-mvc22\net462-mvc22\bin\Debug\net462\net462-mvc22.dll" "/output:bin\Debug\net462\swagger.json"" exited with code -1. [C:\projects\nswag-issue-mvc22\net462-mvc22\net462-mvc22.csproj]

I assume that this is related to assembly loading once again, probably the assembly that contains the IServiceCollection interface got loaded into a different load context or something like that. I did try to dig around NSwag sources but unfortunately failed to find a fix.

[RicoSuter]

Created a PR to fix this: https://github.com/RicoSuter/NSwag/pull/2096

[quails4Eva]

I’ve been getting this exception with .Net 4.7.2 and MVC 2.1.3, though I haven’t tried with such a small repro yet so it’s possible it could be caused by some other factor.