using System;

using AutoMapper;

​

public class One 

{

  public int A {get; set;}

  public int B {get; set;}

  public int C {get; set;}

}

​

public class Two

{

  public int Sum {get; set;} //sum = a + b +c ;

}

​

public class Program

{

    public static void Main()       

    {

        var config = new MapperConfiguration(cfg => { 

            cfg.CreateMap<One, Two>()

             .ForMember(dest => dest.Sum, m => m.MapFrom(src => src.A + src.B + src.C));                                         

        });

        IMapper mapper = config.CreateMapper();

​

        var one = new One

        {

            A = 1,

            B = 2,

            C = 3

        };

        var two = mapper.Map<Two>(one);

        Console.WriteLine(two.Sum);

    }

}