Automapper UseDestinationValue not working

Question

currently struggling with setting of automapper between same classes. The thing is I need to get the entity from db using NHibernate before calling the SaveOrUpdate(). I am then replacing all the properties except Id and LocationId.

Mapper:

public Domain.DomainObjects.Entities.MeetingRoom MapFrom(Domain.DomainObjects.Entities.MeetingRoom input)
        {
            if (!initialized)
            {
                lock (Sync)
                {
                    if (!initialized)
                    {
                        Mapper.CreateMap<Domain.DomainObjects.Entities.MeetingRoom, Domain.DomainObjects.Entities.MeetingRoom>()
                .ForMember(x => x.Id, opt => opt.UseDestinationValue())
                .ForMember(x => x.LocationId, opt => opt.UseDestinationValue());

                        initialized = true;
                    }
                }
            }

            if (input == null)
            {
                throw new NullReferenceException("MeetingRoom is not set!");
            }

            var result = (Domain.DomainObjects.Entities.MeetingRoom)Mapper.Map(input, input.GetType(), typeof(Domain.DomainObjects.Entities.MeetingRoom));

            return result;
        }

Usage of mapper

using (ITransaction t = NHibernateSession.Current.BeginTransaction())
{
    var m = meetingRoomRepository.FindAll(new MeetingRoomByEmailSpecification(meetingRoom.Email)).FirstOrDefault();

    m = meetingRoomMapper.MapFrom(meetingRoom);

    meetingRoomRepository.SaveOrUpdate(m);

    t.Commit();
}

when I am debugging the code I can see that m has the locationId and Id filled but after mapper its being overwriting with the locationId and Id of the meetingRoom (which is 0 by default).

Why not just ignore them? CreateMap().ForMember(x => x.Blarg, opt => opt.Ignore()); — nestedl00p, Sep 20 '17 at 20:30

Sam I am says Reinstate Monica · Accepted Answer · 2017-09-20T20:39:50.197

4

Look at the line you're using to map.

m = meetingRoomMapper.MapFrom(meetingRoom);

you're taking the result of meetingRoomMapper.MapFrom(meetingRoom) and assigning it to m. The problem is, that there's no way for meetingRoomMapper.MapFrom to even know about the properties of m. You can't expect a line that looks like m = ... to not replace the whole object represented by m.

Instead, You should look for a mapping function that takes a destination object as one of it's arguments.

m = Mapper.Map(meetingRoom, m);

edited Sep 20 '17 at 20:39

answered Sep 20 '17 at 20:17

Sam I am says Reinstate Monica

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updated my question with more code. I am already calling the `Mapper.Map(src, dst)` but not sure if in a proper way... – pandemic Sep 20 '17 at 20:26
@pandemic you need to be able to pass `m` into your `MapFrom` method if you want to keep any of the value on `m`, and then pass `m` into `Mapper.Map()` as the destination object – Sam I am says Reinstate Monica Sep 20 '17 at 20:31
secondly, the code you posted does not call a `Mapper.Map(src, dst)`, or more accurately, `Map(TSource source, TDestination destination)`. It calls `Map(object source, Type sourceType, Type destinationType)` – Sam I am says Reinstate Monica Sep 20 '17 at 20:34
your last comment has made it clear for me! thanks a lot Sam – pandemic Sep 20 '17 at 20:42

Automapper UseDestinationValue not working

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