Automapper walking down relationships - automapper

Question

I'm still trying to wrap my head around how automapper works. I have the EF Core query below, which I'd like to change to using automapper.
var query = from t in Context.Tririga.AsNoTracking()
let l = t.Building
let m = t.Owner
let o = m.Organization
where o.Active
select new MetricBadLabManagerByOrganizationDTO {
CampusName = l.CampusName,
Email = m.Email,
Name = m.Name,
OrgLevel3 = o.ThreeName,
OrgLevel4 = o.FourName,
OrgLevel5 = o.FiveName,
OrgLevel6 = o.SixName,
OrgLevel7 = o.SevenName,
Reason = m.Active == false ? "Inactive Employee" : "Invalid Employee",
SiteName = l.SiteName,
Wwid = m.Wwid
};
return await query.ToArrayAsync();
I'm not sure how to setup a mapper configuration to the DTO type because I can't just go from Tririga to MetricBadLabManagerByOrganizationDTO as it doesn't know how to go down the relationships.

Answer 1

Here is the Getting Started Guide from AutoMapper if you haven't gone through the documentation.
I've recently got a chance to work on a project that uses AutoMapper to translate between persistence models and domain models, and here would be how I set things up:
There are many ways to configure your mappings. I like the Profile Instances method:
using AutoMapper;
namespace Company.Product.Infrastructure.Mapping.AutoMapper
{
public class MappingProfile : Profile
{
public MappingProfile()
{
CreateMap<Tririga, MetricBadLabManagerByOrganizationDTO>()
.ForMember(dest => dest.CampusName,
opts => opts.MapFrom(src => src.Building.CampusName))
.ForMember(dest => dest.Email,
opts => opts.MapFrom(src => src.Owner.Email))
.ForMember(dest => dest.Name,
opts => opts.MapFrom(src => src.Owner.Name))
...
}
}
}
There is a whole section about flattening on AutoMapper documentation.
Just a note,
When you configure a source/destination type pair in AutoMapper, the configurator attempts to match properties and methods on the source type to properties on the destination type. If for any property on the destination type a property, method, or a method prefixed with “Get” does not exist on the source type, AutoMapper splits the destination member name into individual words (by PascalCase conventions).
So you might not need to define the rule for each single property you want to map, otherwise what's the point of using AutoMapper.
For example, if your MetricBadLabManagerByOrganizationDTO campus name were named as BuildingCampusName, AutoMapper would be smart enough to look for Building property on your source and see if there is a property called CampusName inside.
There are just lots of valuable information in AutoMapper documentation you can find and learn from, which is what I like!