AutoMapper and Sorting the child collection conditionally

Question

I have an object graph that I'm loading from a database using Fluent NHibernate and AutoMapper into DTOs:-

public class Foo
{
  public int Id { get; set; }
  public virtual ICollection<Bar> Bars { get; set; }
  public bool SortBarByName
}

public class Bar
{
  public int Id { get; set; }
  public int SortOrder { get; set; }
  public virtual Foo Foo { get; set; }
}

My mappings look like:-

public class FooDto
{
  public IEnumerable<BarDto> Bars { get; set; }
}

public class BarDto
{
  public string Name { get; set; }
  public int SortOrder { get; set; }
}

My mapping looks like:

mapper.CreateMap<Foo, FooDto>().ForMember(d => d.Bars, o => o.MapFrom(s => s.Bars));
mapper.CreateMap<Bar, BarDto>();

When I return FooDto, I want collection of BarDto to be sorted based on below condition. I want to sort BarDto by Name if SortBarByName is true or by SortOrder if SortBarByName is false, based on SortBarByName property of class Foo.

Note: Name property is not present in Bar class, it is only in BarDto.

Can I do something in the AutoMappers to achieve this?

Answer 1

Since one of the properties you want to use for the order is only available after you mapped the data you can use the AfterMap() functionality of AutoMapper like this:

mapper.CreateMap<Foo, FooDto>()
                .AfterMap(
                    (foo, dto) =>
                    {
                        dto.Bars = foo.SortBarByName
                            ? dto.Bars.OrderBy(x => x.Name)
                            : dto.Bars.OrderBy(x => x.SortOrder);
                    });

This should order the Bars after all data is available.