using System;

using System.Collections.Generic;   

using System.Linq;  

using AutoMapper;

using AutoMapper.Configuration;

using AutoMapper.Mappers;

public class Program

{

    public static void Main()

    {

        var config = new MapperConfiguration(

            cfg => 

            cfg.CreateMap<BookVM, BookEM>()

                .ForMember(

                    dest=>dest.Autors,

                    opt=> opt.MapFrom(

                        src=>src.Ids

                        .Select(b=>new Autor{Id = b} )

                    )

                )

        );

        var mapper = config.CreateMapper();

        var a= mapper.Map<BookEM>(

            new BookVM()

            {

                Ids = new long[]{1,2}

            }

        );

        Console.WriteLine(a.Autors.First().Id);

    }

}

class BookVM

{

  public IEnumerable<long> Ids {get;set;}

}

class BookEM

{

  public IEnumerable<Autor> Autors {get;set;}

}

class Autor

{

  public long Id {get;set;}

}