Self referencing loop causing stack overflow with map

Question

According to the documentation PreserveReferences should be set automatically whenever possible for AutoMapper.

Starting from 6.1.0 PreserveReferences is set automatically at config time whenever possible.

https://github.com/AutoMapper/AutoMapper/wiki/5.0-Upgrade-Guide

I have also tried setting MaxDepth to 1 but I still get a stack overflow exception with the following mapping. Can I get around this somehow or do I need to modify the view models?

cfg.CreateMap<ArticleViewModel, Article>(MemberList.Source)
    .MaxDepth(1)
    .EqualityComparison((src, dst) => src.Id == dst.Id);

Code that causes the stack overflow exception:

var article = await iArticleRepository.GetAsync(id);
//The mapping below causes the exception
var mappedArticle = Mapper.Map<ArticleViewModel>(article);

Entities:

public class Article: IEntity<int>
{
    [Key]
    public int Id { get; set; }

    ...

    public int SupplierId { get; set; }

    public virtual Supplier Supplier { get; set; }
}

public class Supplier: IEntity<int>
{
    [Key]
    public int Id { get; set; }

    ...

    public virtual ICollection<Contact> Contacts { get; set; }
}

public class Contact: IEntity<int>
{
    [Key]
    public int Id { get; set; }

    ...
    public virtual ICollection<Supplier> Suppliers { get; set; }
}

View models:

public class ArticleViewModel
{
    public int Id { get; set; }

    ...
    public SupplierViewModel Supplier { get; set; }

}

public class SupplierViewModel
{
    public int Id { get; set; }

    ...
    public List<ContactViewModel> Contacts { get; set; }

}

public class ContactViewModel
{
    public int Id { get; set; }
    ... 
    public List<SupplierViewModel> Suppliers { get; set; }
}

Your Contact entity has a collection of other Contacts while your ContactViewModel has a collection of SuplierViewModels. Is that correct? — Fabiano, Jul 20 '17 at 12:42
@Fabiano Thanks for noticing and no it should of course be Suppliers. Updated now. — Ogglas, Jul 20 '17 at 12:44
Hopefully for people who have hundreds of CreateMap (like us) it is possible to add PreserveReferences for all maps with one single line of code : cfg.ForAllMaps((typeMap, mappingExpression) => mappingExpression.PreserveReferences()); Unfortunately doing so we won't benefits of performance improvement. — bN_, Oct 19 '17 at 12:42

score 3 · Accepted Answer · edited Jul 20 '17 at 13:55

Well, it's unclear what does whenever possible mean. Since the documentation before that states

It turns out this tracking is very expensive, and you need to opt-in using PreserveReferences for circular maps to work

looks like your scenario fails into not possible category :)

Let not rely on that and use the explicit opt-in. The circular reference in this sample model is between Supplier and Contact, so you have to specify in one of the involved class mappings, for instance:

cfg.CreateMap<ArticleViewModel, Article>(MemberList.Source)
    .MaxDepth(1)
    .EqualityComparison((src, dst) => src.Id == dst.Id);

cfg.CreateMap<SupplierViewModel, Supplier>(MemberList.Source)
    .PreserveReferences()
    .EqualityComparison((src, dst) => src.Id == dst.Id);

Thanks. I tried with this before but without MaxDepth. When using both however it worked! Will update your answer and mark as accepted. — Ogglas, Jul 20 '17 at 13:54

Self referencing loop causing stack overflow with map

1 Answers1