How to register multiple implementations of the same interface in Asp.Net Core?

Question

I have services that are derived from the same interface.

public interface IService { }
public class ServiceA : IService { }
public class ServiceB : IService         


        

Answer 1

since my post above, I have moved to a Generic Factory Class

Usage

 services.AddFactory()
         .Add("A")
         .Add("B");

 public MyClass(IFactory processorFactory)
 {
       var x = "A"; //some runtime variable to select which object to create
       var processor = processorFactory.Create(x);
 }

Implementation

public class FactoryBuilder where I : class
{
    private readonly IServiceCollection _services;
    private readonly FactoryTypes _factoryTypes;
    public FactoryBuilder(IServiceCollection services)
    {
        _services = services;
        _factoryTypes = new FactoryTypes();
    }
    public FactoryBuilder Add(P p)
        where T : class, I
    {
        _factoryTypes.ServiceList.Add(p, typeof(T));

        _services.AddSingleton(_factoryTypes);
        _services.AddTransient();
        return this;
    }
}
public class FactoryTypes where I : class
{
    public Dictionary ServiceList { get; set; } = new Dictionary();
}

public interface IFactory
{
    I Create(P p);
}

public class Factory : IFactory where I : class
{
    private readonly IServiceProvider _serviceProvider;
    private readonly FactoryTypes _factoryTypes;
    public Factory(IServiceProvider serviceProvider, FactoryTypes factoryTypes)
    {
        _serviceProvider = serviceProvider;
        _factoryTypes = factoryTypes;
    }

    public I Create(P p)
    {
        return (I)_serviceProvider.GetService(_factoryTypes.ServiceList[p]);
    }
}

Extension

namespace Microsoft.Extensions.DependencyInjection
{
    public static class DependencyExtensions
    {
        public static IServiceCollection AddFactory(this IServiceCollection services, Action> builder)
            where I : class
        {
            services.AddTransient, Factory>();
            var factoryBuilder = new FactoryBuilder(services);
            builder(factoryBuilder);
            return services;
        }
    }
}