Okay so I have an issue at the moment which is either down to AutoMapper, my NHibernate query or Domain/DTO design.

The problem I have is that when i do a fetch, for example ObjectA contains a list of ObjectB and ObjectB has a property of its parent ObjectA. When I have a query which does an eager fetch on the ObjectB property of my ObjectA then i can go on infinitely forever A.B.A.b.A.B.A.B and so on.

This means that when I try to map the domain object to DTOA which contains the same deal, DTOA has a list of DTOB and DTOB has a property of its parent DTOA. My services time out when returning this because I believe I m using AutoMapper to map DomainA to DTOA and then because DTOA.DTOB.DTOA.DTOB etc is populated its infinitely serialising.

Anyway whats the best solution to what I m sure is an age old classic issue but I m struggling to find the right things to type into my old friend google. Can I get AutoMapper to ignore the parent instance in the child, preferrably even I think if i could get Nhibernate to fetch the list but keep a proxy on the parent property. The worst solution would be a domain object change with objects for specific scenarios or speical logic.

Any help appreciated thanks.

EDIT - CODE

Mapping code

 Mapper.CreateMap<DTOA, DomainA>();
        Mapper.CreateMap<DomainA, DTOA>()
            .ForMember(dst => dst.AProperty,
                       opts =>
                       opts.ResolveUsing<LazyLoadResolver>().FromMember(src => src.AProperty));

Domain object DomainA

 /// <summary>
    /// Data Transfer Object, object representing a user
    /// </summary>
    public class DomainA
    {
        /// <summary>
        /// Gets or sets the clans.
        /// </summary>
        /// <value>The clans.</value>
        public virtual IList<DomainB> AProperty{ get; set; }
}

Domain object DomainB

/// <summary>
/// DTO for clan members
/// </summary>
public class DomainB
{
    /// <summary>
    /// Gets or sets the ID.
    /// </summary>
    /// <value>The ID.</value>
    public virtual int ID { get; set; }

    /// <summary>
    /// Gets or sets the user.
    /// </summary>
    /// <value>The user.</value>
    public virtual DomainA BProperty{ get; set; }

}

Nhibernate query

return session.QueryOver<DomainA>()
                .Where(a => a.ID == id)
                .Fetch(a=> a.AProperty).Eager
                .List<DomainA>().FirstOrDefault();

WCF Service return statement

return AutoMapper.Map<DomainA, DTOA>(returnedDomainA);

Running that query with fetching and that dto domain structure and auto mapper configuration means my services times out with no errors, I assume as its trying to serialise and is endlessly looping, without the fetch and the list being null, all works fine of course