c# - Possible to use AutoMapper to map one object to list of objects?

Question

These are my classes:

public class EventLog {
        public string SystemId { get; set; }
        public string UserId { get; set; }
        public List<Event> Events { get; set; }
}

public class Event {
        public string EventId { get; set; }
        public string Message { get; set; }
}

public class EventDTO {
        public string SystemId { get; set; }
        public string UserId { get; set; }
        public string EventId { get; set; }
        public string Message { get; set; }
}

Basically I need to go from a single object, with a nested list, to a list of objects with values from the nested list and the parent object. Can this be done in AutoMapper? I realize that I can easily map the Events list and get a list of EventDTO objects and then manually set the SystemId and UserId, it would just be very convenient to let AutoMapper handle it for me.

Answer 1

您将需要这三个映射和一个自定义转换器：

Mapper.CreateMap<Event, EventDTO>(); // maps message and event id
Mapper.CreateMap<EventLog, EventDTO>(); // maps system id and user id
Mapper.CreateMap<EventLog, IEnumerable<EventDTO>>()
      .ConvertUsing<EventLogConverter>(); // creates collection of dto

Event因此，您配置了从到EventDTO和从EventLog到的映射，EventDTO您可以在自定义转换器中使用它们：

class EventLogConverter : ITypeConverter<EventLog, IEnumerable<EventDTO>>
{
    public IEnumerable<EventDTO> Convert(ResolutionContext context)
    {
        EventLog log = (EventLog)context.SourceValue;
        foreach (var dto in log.Events.Select(e => Mapper.Map<EventDTO>(e)))
        {
            Mapper.Map(log, dto); // map system id and user id
            yield return dto;
        }
    }
}

NBuilder示例代码：

var log = new EventLog {
    SystemId = "Skynet",
    UserId = "Lazy",
    Events = Builder<Event>.CreateListOfSize(5).Build().ToList()
};

var events = Mapper.Map<IEnumerable<EventDTO>>(log);