AutoMapper ProjectTo: Not working with nested objects

Question

I have the following dto:

public class SingleForm
{
    // other props left out for brevity

    public List<Filter> Filters { get; set; }
}

I then try mapping it with AutoMapper like so:

CreateMap<Form, SingleForm>()
    .ForMember(dest => dest.Filters, 
        opts => opts.MapFrom(src => 
            Mapper.Map<List<Filter>>(src.Questions)));

CreateMap<FormQuestion, Filter>()
    .ForMember(dest => dest.Header, 
        opts => opts.MapFrom(src => src.Question.QuestionText));

I then use ProjectTo:

var query = this.context.Forms
    .Where(e => e.Id == message.FormId)
    .ProjectTo<SingleForm>()
    .FirstOrDefault();

However, my filters collection is empty when I execute the query.

When I try to manually map the collection using LINQ, like below, it works correctly, so I'm wondering if I am doing something wrong?

var query = this.context.Forms
    .Where(e => e.Id == message.FormId)
    .Select(e => new SingleForm
    {
        Id = e.Id,
        Filters = e.Questions.Select(q =>
            new Filter { 
                Header = q.Question.QuestionText 
        }).ToList()
    })
    .FirstOrDefault();

SpruceMoose · Accepted Answer · 2017-10-24 09:19:39Z

3

In general, I think it is best to avoid calling Mapper.Map() within your profile configuration. With this in mind, I think changing your first mapping to the following may help:

CreateMap<Form, SingleForm>()
    .ForMember(dest => dest.Filters,
        opts => opts.MapFrom(src => src.Questions));

edited Oct 24, 2017 at 9:19

answered Oct 24, 2017 at 9:09

SpruceMoose

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Comments

user3732365 · Accepted Answer · 2017-10-24 10:16:03Z

0

If the mapping happens out side DbContext then should using includes method to retrieve all relationships items which nit able to lazy load without DbContext.

answered Oct 24, 2017 at 10:16

user3732365

1 Comment

SpruceMoose Over a year ago

That's kind of the point of ProjectTo() - see Automapper Queryable Extensions

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