Using Automapper ValueResolver for complex, reusable mapping

Tuesday, October 23, 2012
Automapper is a great tool to help automate the tedious task of mapping Domain Model to View Model and back.  However, sometimes, mappings are not as straightforward as a simple one to one, left to right mapping.  The example below is a real-world implementation of ValueResolver for mapping date of birth to age:

using System;
using AutoMapper;

namespace SomeCompany.SomeProject.Web.Models.ValueResolvers
{
    public class AgeValueResolver : ValueResolver<DateTime?, int>
    {
        protected override int ResolveCore(DateTime? dateOfBirth)
        {
            if (dateOfBirth.HasValue)
            {
                var age = DateTime.Today.Year - dateOfBirth.Value.Year;

                if (dateOfBirth.Value > DateTime.Today.AddYears(-age))
                {
                    age--;
                }

                return age;
            }

            return 0;
        }
    }
}

To use this within your mapping, you could do something like:

CreateMap<IPerson, PersonViewModel>()
  .ForMember(dest => dest.Age, opt => opt.ResolveUsing<AgeValueResolver>().FromMember(src => src.DOB));