app.MapControllers() => ReflectionTypeLoadException. Could not load type 'Microsoft.OpenApi.Any.IOpenApiAny' from assembly 'Microsoft.OpenApi

[bartvanhoey]

In the Program.cs file of a .Net 9 Core API project the line app.MapControllers throws an ReflectionTypeLoadException.
This happens as of version Microsoft.OpenApi 2.0.0-preview1. Microsoft.OpenApi 1.6.23 does NOT throw an Exception.

System.Reflection.ReflectionTypeLoadException: Unable to load one or more of the requested types.
Could not load type 'Microsoft.OpenApi.Any.IOpenApiAny' from assembly 'Microsoft.OpenApi, Version=2.0.0.0, Culture=neutral, PublicKeyToken=3f5743946376f042'.
at System.Reflection.RuntimeModule.GetDefinedTypes()
at Microsoft.AspNetCore.Mvc.Controllers.ControllerFeatureProvider.PopulateFeature(IEnumerable1 parts, ControllerFeature feature) at Microsoft.AspNetCore.Mvc.ApplicationParts.ApplicationPartManager.PopulateFeature[TFeature](TFeature feature) at Microsoft.AspNetCore.Mvc.ApplicationModels.ControllerActionDescriptorProvider.GetControllerTypes() at Microsoft.AspNetCore.Mvc.ApplicationModels.ControllerActionDescriptorProvider.GetDescriptors() at Microsoft.AspNetCore.Mvc.ApplicationModels.ControllerActionDescriptorProvider.OnProvidersExecuting(ActionDescriptorProviderContext context) at Microsoft.AspNetCore.Mvc.Infrastructure.DefaultActionDescriptorCollectionProvider.UpdateCollection() at Microsoft.AspNetCore.Mvc.Infrastructure.DefaultActionDescriptorCollectionProvider.Initialize() at Microsoft.AspNetCore.Mvc.Infrastructure.DefaultActionDescriptorCollectionProvider.GetChangeToken() at Microsoft.Extensions.Primitives.ChangeToken.ChangeTokenRegistration1..ctor(Func1 changeTokenProducer, Action1 changeTokenConsumer, TState state)
at Microsoft.Extensions.Primitives.ChangeToken.OnChange(Func`1 changeTokenProducer, Action changeTokenConsumer)
at Microsoft.AspNetCore.Mvc.Routing.ActionEndpointDataSourceBase.Subscribe()
at Microsoft.AspNetCore.Builder.ControllerEndpointRouteBuilderExtensions.GetOrCreateDataSource(IEndpointRouteBuilder endpoints)
at Microsoft.AspNetCore.Builder.ControllerEndpointRouteBuilderExtensions.MapControllers(IEndpointRouteBuilder endpoints)
at Program.

$(String[] args) in C:\Data\MyGitHubRepos\Net9Authentication\Net9Auth.API\Program.cs:line 76
System.TypeLoadException: Could not load type 'Microsoft.OpenApi.Any.IOpenApiAny' from assembly 'Microsoft.OpenApi, Version=2.0.0.0, Culture=neutral, PublicKeyToken=3f5743946376f042'.

[MaggieKimani1]

@bartvanhoey this error is as a result of a breaking change we've introduced in v2.0 of the lib.
We've gotten rid of the IOpenApiAny type and replaced it with JsonNode to model examples and extensions for compatibility with JSON schema types.

Here's a link to the release notes that can help you fix the breaking change: https://github.com/microsoft/OpenAPI.NET/releases/tag/2.0.0-preview1