Question

I have a problem with NHibernate for a longtime which I solved by non-optimal ways/workarounds.

First of all, I’m using WCF REST to communicate with my client application. As you know, serializing persisted entities is not a best practise and always causes other problems. Thus, I always map my entities to DTO’s with NHibernates Transformers. The problem is that I have entities which are more complex to use Transformers to convert them.

How can I map sub entities to sub dto’s by using transformers or any other nhibernate feature?

Note: I don’t want to use 3rd parties like Automapper.

These are the Entities and DTO’s which I want to map. Variable names are exactly same with each other.

Entity Classes:

EntityType

public class crmEntityType : EntityModel<crmEntityType>
{
    public crmEntityType()
    {
        Association = new List<crmEntityType>();
        Fields = new List<crmCustomField>();
    }

    public virtual int ID { get; set; }

    public virtual string Title { get; set; }

    public virtual ICollection<crmEntityType> Associations { get; set; }

    public virtual ICollection<crmCustomField> Fields { get; set; }

}

CustomFields

    public class crmCustomField : EntityModel<crmCustomField>
{
    public virtual int ID { get; set; }

    public virtual string Name { get; set; }

    public virtual crmEntityType EntityType { get; set; }
}

DTO’s

EntityTypeDTO

[DataContract]
public class EntityTypeDTO
{
    [DataMember]
    public int ID { get; set; }

    [DataMember]
    public string Title { get; set; }

    [DataMember]
    public IList<CustomFieldDTO> Fields { get; set; }

    [DataMember]
    public int[] Associations { get; set; }
}

CustomFieldDTO

[DataContract]
    public class CustomFieldDTO
{
    [DataMember]
    public int ID { get; set; }

    [DataMember]
    public string Name { get; set; }

    [DataMember]
    public int EntityType { get; set; }

    [DataMember]
    public int FieldType { get; set; }

}

Answer 1

I found my solution by spending my day and night to work it out. Finally, I’ve got the best solution I could find. I hope it helps someone in my condition some day.

This linq query works with just one database round-trip. I think it maps the classes in memory.

return (from entityType in Provider.GetSession().Query<crmEntityType>()
                .Fetch(x => x.Association)
                .Fetch(x => x.Fields)
                .AsEnumerable()
    select new EntityTypeDTO()
    {
        ID = entityType.ID,
        Title = entityType.Title,
        Association = entityType.Association.Distinct()
                               .Select(asc => asc.ID).ToArray<int>(),
        Fields = entityType.Fields.Distinct()
                               .Select(fi => new CustomFieldDTO 
                                            { ID = fi.ID, 
                                              Name = fi.Name, 
                                              Value = fi.Value, 
                                              EntityType = fi.EntityType.ID,
                                              Type = fi.Type 
                                            }).ToList()
    }).ToList();