fluent nhibernate one to many mapping
- by Sammy
I am trying to figure out what I thought was just a simple one to many mapping using fluent Nhibernate. I hoping someone can point me to the right directory to achieve this one to many relations
I have an articles table and a categories table
Many Articles can only belong to one Category
Now my Categores table has 4 Categories and Articles has one article associated with cateory1
here is my setup.
using FluentNHibernate.Mapping;
using System.Collections;
using System.Collections.Generic;
namespace FluentMapping
{
public class Article
{
public virtual int Id { get; private set; }
public virtual string Title { get; set; }
public virtual Category Category{get;set;}
}
public class Category
{
public virtual int Id { get; private set; }
public virtual string Description { get; set; }
public virtual IList<Article> Articles { get; set; }
public Category()
{
Articles=new List<Article>();
}
public virtual void AddArticle(Article article)
{
article.Category = this;
Articles.Add(article);
}
public virtual void RemoveArticle(Article article)
{
Articles.Remove(article);
}
}
public class ArticleMap:ClassMap<Article>
{
public ArticleMap()
{
Table("Articles");
Id(x => x.Id).GeneratedBy.Identity();
Map(x => x.Title);
References(x => x.Category).Column("CategoryId").LazyLoad();
}
public class CategoryMap:ClassMap<Category>
{
public CategoryMap()
{
Table("Categories");
Id(x => x.Id).GeneratedBy.Identity();
Map(x => x.Description);
HasMany(x => x.Articles).KeyColumn("CategoryId").Fetch.Join();
}
}
}
}
if I run this test
[Fact]
public void Can_Get_Categories()
{
using (var session = SessionManager.Instance.Current)
{
using (var transaction = session.BeginTransaction())
{
var categories = session.CreateCriteria(typeof(Category))
//.CreateCriteria("Articles").Add(NHibernate.Criterion.Restrictions.EqProperty("Category", "Id"))
.AddOrder(Order.Asc("Description"))
.List<Category>();
}
}
}
I am getting 7 Categories due to Left outer join used by Nhibernate
any idea what I am doing wrong in here?
Thanks
[Solution]
After a couple of hours reading nhibernate docs I here is what I came up with
var criteria = session.CreateCriteria(typeof (Category));
criteria.AddOrder(Order.Asc("Description"));
criteria.SetResultTransformer(new DistinctRootEntityResultTransformer());
var cats1 = criteria.List<Category>();
Using Nhibernate linq provider
var linq = session.Linq<Category>();
linq.QueryOptions.RegisterCustomAction(c => c.SetResultTransformer(new DistinctRootEntityResultTransformer()));
var cats2 = linq.ToList();
