Open generic service type 'MediatR.Pipeline.IRequestPreProcessor`1[TRequest]' requires registering an open generic implementation type

[tomasaschan]

I tried working around #28 by implementing my behavior as a pre-processor instead (the actual behavior is validation, so this fits well with my use-case anyway), but now the application fails to start, with the following error:

Unhandled Exception: System.ArgumentException: Open generic service type 'MediatR.Pipeline.IRequestPreProcessor`1[TRequest]' requires registering an open generic implementation type.
Parameter name: descriptors
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteFactory.Populate(IEnumerable`1 descriptors)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteFactory..ctor(IEnumerable`1 descriptors)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider..ctor(IEnumerable`1 serviceDescriptors, ServiceProviderOptions options)
   at Microsoft.Extensions.DependencyInjection.ServiceCollectionContainerBuilderExtensions.BuildServiceProvider(IServiceCollection services, ServiceProviderOptions options)
   at Microsoft.Extensions.DependencyInjection.ServiceCollectionContainerBuilderExtensions.BuildServiceProvider(IServiceCollection services)
   at Microsoft.AspNetCore.Hosting.Internal.WebHost.BuildApplication()
   at Microsoft.AspNetCore.Hosting.WebHostBuilder.Build()
   at Web.Program.BuildWebHost(String[] args) in C:\Work\my-project\Web\Program.cs:line 21
   at Web.Program.Main(String[] args) in C:\Work\my-project\Web\Program.cs:line 17

The service registration is, as before, just services.AddMediatR(typeof(FooHandler)), and the implementation of the pre-processor is

public class FooPreProcessor : IRequestPreProcessor<FooCommand>
{
    public Task Process(FooCommandrequest, CancellationToken cancellationToken)
    {
        throw new NotImplementedException();
    }
}

Am I missing something here, or is this the same problem as #12?

[jbogard]

Yes, same problem