registering multiple instances in .Net Core IOC

Question

I have a base class with multiple implementations and I would like to be able to register all the implementations in a look similar to Registering by Convention.

I am able to get all the implementations of the base class but when I try to actually register them I get the following exception:

System.ArgumentException: 'Open generic service type 'Bento.SearchContent.EventListener.Infrastructure.Index`1[T]' requires registering an open generic implementation type.'

public abstract class Index<T>
    where T : class
{
   ....        
}

sample subclass:

public class SurveyChangedIndex : Index<SurveyChanged>
{
   ....
}

sample function:

public static void RegisterIndexing()
        {
            var indexBase = typeof(Index<>);
            GetAllDescendantsOf(Assembly.GetAssembly(indexBase), indexBase)
                .ForEach(indexType => { _serviceCollection.AddSingleton(indexBase, indexType); });

            _serviceCollection.AddTransient<IIndexResolver, IndexResolver>(sp => new IndexResolver(sp));
        }

You may want to add the asp.net-core tag. .NET Core isn't just for ASP.NET... — Jon Skeet
– Jon Skeet, Commented Jan 15, 2018 at 17:33
Basically, the standard IoC is very basic and requires you to register all of the different type variants separately. — juunas
– juunas, Commented Jan 15, 2018 at 19:05

Farhad-Taran · Accepted Answer · 2018-01-15 22:04:02Z

The following although not pretty works.

using Microsoft.Extensions.DependencyInjection;
using System;
using System.Linq;
using System.Reflection;

namespace ConsoleApp3
{
    public class Index<T> where T : class { }

    public class A { }

    public class AIndex : Index<A> { }

    public class B { }

    public class BIndex : Index<B> { }

    class Program
    {

        static void Main(string[] args)
        {
            IServiceCollection serviceCollection = new ServiceCollection();

            new Type[] { typeof(AIndex), typeof(BIndex) }.ToList()
                .ForEach(t =>
                {
                    serviceCollection.AddSingleton(typeof(Index<>).MakeGenericType(t.BaseType.GetGenericArguments()), t);
                });

            var sp = serviceCollection.BuildServiceProvider();
            var aIndex = sp.GetService(typeof(Index<A>));
            var bIndex = sp.GetService(typeof(Index<B>));
        }
    }
}

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