using Autofac;

using Autofac.Features.Variance;

using DryIoc;

using System;

using System.Collections.Generic;

​

namespace DiVariance

{

    public interface IQuery<in TIn, out TOut>

    {

        IReadOnlyCollection<TOut> Get(TIn key);

    }

​

    public class FakeRepository : IQuery<object, string>

    {

        public IReadOnlyCollection<string> Get(object key)

        {

            return new[] { key.ToString() };

        }

    }

​

    public class Program

    {

        public static void Main(string[] args)

        {

            IQuery<string, object> service;

​

            service = new FakeRepository(); // This works fine

            Console.WriteLine("Poor man's IoC: {0}", string.Join(",", service.Get("42")));

​

            try

            {

                var autofacBuilder = new Autofac.ContainerBuilder();

                autofacBuilder.RegisterSource(new ContravariantRegistrationSource());

                autofacBuilder.RegisterAssemblyTypes(typeof(FakeRepository).Assembly).AsImplementedInterfaces();

                service = autofacBuilder.Build().Resolve<IQuery<string, object>>(); // unable to resolve

                Console.WriteLine("Autofac: {0}", string.Join(",", service.Get("42")));

            }

            catch (Exception ex)

            {

                Console.WriteLine(ex);

            }

​

            try

            {

                var dryIocContainer = new DryIoc.Container();

                dryIocContainer.RegisterMany(new[] { typeof(FakeRepository).Assembly });

                var service1 = dryIocContainer.Resolve<IQuery<string, object>>(); // unable to resolve

                Console.WriteLine("DryIoc: {0}", string.Join(",", service1.Get("42")));

            }

            catch (Exception ex)

            {

                Console.WriteLine(ex);

            }

        }

    }

}

​