using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var executor = new ConverterExecutor();

        executor.RegisterConverter(new DestinationConverter());

        var result = executor.ConvertMultiple(new List<SharedBaseClass>{new InputClass()});

        Console.WriteLine(result.First());

    }

}

​

public class SharedBaseClass {}

​

public class DestinationClass : SharedBaseClass {

    public DestinationClass(){}

}

​

public class InputClass : SharedBaseClass {

    public InputClass(){}

}

​

public interface IConverter<out TU, T> where TU : SharedBaseClass where T: SharedBaseClass

{

    public TU Convert(T input);

}

​

public class DestinationConverter: IConverter<DestinationClass, InputClass> {

    public DestinationClass Convert(InputClass input) {

        return new DestinationClass();

    }

}

​

public class ConverterExecutor

{

    private readonly Dictionary<Type, Func<SharedBaseClass, SharedBaseClass>> _converters = new();

    public void RegisterConverter<TU, T>(IConverter<TU, T> converter) where TU : SharedBaseClass where T : SharedBaseClass

    {

        _converters[typeof(T)] = x => converter.Convert((T)x);  

    }

    public IEnumerable<SharedBaseClass> ConvertMultiple(IEnumerable<SharedBaseClass> classesToConvert)

    {

        var converted = new List<SharedBaseClass>();

        foreach(var toConvert in classesToConvert)

        {

            _converters.TryGetValue(toConvert.GetType(), out var converter);

            if (converter != null) {

                converted.Add(converter(toConvert));

                continue;

            }

            converted.Add(toConvert);

        }

        return converted;

    }

}