using System;

using System.Collections.Generic;

using AutoMapper;

​

public class Program

{

    public static void Main()

    {

        var configuration = new MapperConfiguration(cfg =>

        {

            cfg.CreateMap<A, ADto>().ForMember(

                dest => dest.Flag, 

                opt => opt.MapFrom(src =>

                    src.MyProperty / 3 == 1)); /* DO MAPPING HERE */

        });

        configuration.AssertConfigurationIsValid();

        var mapper = configuration.CreateMapper();

        var aList = new List<A> {  new A { MyProperty = 1 }, new A { MyProperty = 2 }, new A { MyProperty = 3 } };

        var results = mapper.Map<IEnumerable<ADto>>(aList);

        foreach (var result in results) {

            Console.WriteLine($"MyProperty: {result.MyProperty}, Flag: {result.Flag}");

        }

    }

​

    class A

    {

        public int MyProperty { get; set; }

    }

​

    class ADto

    {

        public int MyProperty { get; set; }

​

        public bool Flag { get; set; }

    }

}