Fluent NHibernate One-To-Many Mapping

Question

I have the following 2 classes: Advert ``` public virtual int Id { get; set; public virtual IList AdvertImages { get; set; } ``` AdvertImage ``` public virtual int Id { get; set; } public virtual string Filename { get; set; public virtual Advert Advert { get; set; } ``` In the DB, my AdvertImages table has the FK 'AdvertId' which relates to the Adverts table which has the PK of 'Id'. This is a One-To-Many mapping, in that one advert can have many images. My Fluent NHibernate mappings (edited for brevity) are: AdvertMap ``` Id(x => x.Id) .GeneratedBy.Identity(); ... HasMany(x => x.AdvertImages) .KeyColumn("AdvertId") .Inverse(); ... Table("Adverts"); ``` AdvertImageMap ``` Id(x => x.Id) .GeneratedBy.Identity(); ... References(x => x.Advert) .Column("AdvertId"); ... Table("AdvertImages"); ``` I am creating a new instance of `Advert` in code, then populating the `AdvertImages` property (of Advert) with a `List`. When I go to persist my `Advert` object to the DB,…

Accepted Answer

You need to change your `Advert` mapping to cascade:

```
Id(x => x.Id)
  .GeneratedBy.Identity();

HasMany(x => x.AdvertImages)
  .KeyColumn("AdvertId")
  .Inverse()
  .Cascade.AllDeleteOrphan();

Table("Adverts");
```

You should then be able to do something like this to persist an `Advert` object and it's children `AdvertImage`.

```
Advert newAdvert = new Advert();
AdvertImage newImage = new AdvertImage();
newImage.Advert = newAdvert;
newAdvert.AdvertImages.Add(newImage);

using(NHibernate.ISession session = SessionFactory.GetCurrentSession())
{
    using (NHibernate.ITransaction tran = session.BeginTransaction())
    {
        session.Save(newAdvert);
        tran.Commit();
    }
}
```

My entities usually contain Add and Remove methods for bidirectional one to many relationships like this:

```
public class Advert
{
    public virtual IList<AdvertImage> AdvertImages { get; set; }

public virtual void AddImage(AdvertImage newImage)
    {
        newImage.Advert = this;
        AdvertImages.Add(newImage);
    }
}
```

Fluent NHibernate One-To-Many Mapping

Solution

Problem