Pre and Post Processors handled multiple times (version 8)

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EDIT: Solution from @lilasquared

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Am I doing something wrong here? This happens using pre and post processors

public class MediatRInstaller : IInstaller
    {
        public void InstallServices(IServiceCollection services, IConfiguration configuration)
        {
            services.AddMediatR(typeof(CreateCustomerCommand).Assembly);

            services.AddScoped(typeof(IRequestPostProcessor<,>), typeof(LoggingBehavior<,>));
        }
    }

public class LoggingBehavior<TRequest, TResponse> : IRequestPostProcessor<TRequest, TResponse>
    {
        public Task Process(TRequest request, TResponse response, CancellationToken cancellationToken)
        {
            Log.Information($"Handled {typeof(TRequest).DeclaringType?.Name ?? typeof(TRequest).Name}");

            return Task.CompletedTask;
        }
    }

After one web request:

08 Jan 2020 10:07:06.507 Handled GetCustomersQuery
08 Jan 2020 10:07:00.679 Handled GetCustomersQuery

[lilasquared]

the AddMediatR method already connects implementations to types closing the pre and post request processors, so you do not need this line services.AddScoped(typeof(IRequestPostProcessor<,>), typeof(LoggingBehavior<,>));

you only need to register actual pipeline behaviors manually.

[lilasquared]

in fact, the main wiki (https://github.com/jbogard/MediatR/wiki#aspnet-core) DOES have this link

ASP.NET Core If you’re using ASP.NET Core then you can skip the configuration and use MediatR’s MediatR.Extensions.Microsoft.DependencyInjection package which includes a IServiceCollection.AddMediatR(Assembly) extension method, allowing you to register all handlers and pre/post-processors in a given assembly.