try to help

myMatching.cs

using System;
using System.Collections.Generic;

namespace index_property
{
    #region resource implementations
    public interface IResourceManager
    {
        void UseSomething();
    }
    public class ResourceRub : IResourceManager
    {
        public void UseSomething()
        {
            Console.WriteLine("Gets RUB");
        }
    }
    public class ResourceEUR : IResourceManager
    {
        public void UseSomething()
        {
            Console.WriteLine("Gets EURO");
        }
    }
    #endregion

    public interface IService
    {
        Action this[string index] { get; }
    }

    public class CurrencyService : IService
    {
        private readonly IDictionary<string, IResourceManager> _values;

        public CurrencyService(IEnumerable<IResourceManager> managers) => _values = FillDictionary(managers);

        private IDictionary<string, IResourceManager> FillDictionary(IEnumerable<IResourceManager> resources)
        {
            var result = new Dictionary<string, IResourceManager>();

            foreach (var resource in resources)
                switch (resource)
                {
                    case ResourceRub rb: result.Add("UsdRub", rb); break;
                    case ResourceEUR re: result.Add("UsdEur", re); break;
                }

            return result;
        }

        public Action this[string index] => _values[index].UseSomething;
    }

    public class ServiceManager
    {
        private readonly IService _cService;
        public ServiceManager(IService service) => _cService = service;

        public IService Foo => _cService;
    }

    class Program
    {
        static void Main(string[] args)
        {
            var managersList = new List<IResourceManager>
            {
                new ResourceRub(),
                new ResourceEUR()
            };

            var cService = new CurrencyService(managersList);
            var serviceManager = new ServiceManager(cService);

            serviceManager.Foo["UsdRub"].Invoke();
            serviceManager.Foo["UsdEur"].Invoke();

            Console.ReadKey();
        }
    }
}

like describe:
C# 7 syntax , indexers, used auto getters a lot of times, the pattern matching.