I seem to be a bit thick as I cant get this to work.

I can get User to work without the collection.


could not insert: [NHiberTest.Objects.Note][SQL: INSERT INTO Notes (Note) VALUES (@p0); select SCOPE_IDENTITY()]

public class User
{
public virtual int ID { get; set; }
public virtual string FirstName { get; set; }
public virtual string LastName { get; set; }
public virtual IList<Note> Notes{ get; set; }

}

public class Note
{
public virtual int ID{get;set;}
public virtual string Text { get; set; }
}

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name="NHiberTest.Objects.User,NHiberTest.Objects" table="[User]">

<id name="ID" column="ID" unsaved-value ="0" type="System.Int32">
<generator class="identity" />
</id>

<property name="FirstName" column="FirstName"/>
<property name="LastName" column ="LastName"/>


<bag generic="true" name="Notes" table="Notes" cascade="all">
<key column="UserID" not-null="true"/>
<one-to-many class ="NHiberTest.Objects.Note,NHiberTest.Objects"/>
</bag>


</class>


</hibernate-mapping>

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name="NHiberTest.Objects.Note,NHiberTest.Objects" table="Notes">

<id name="ID" column="ID" unsaved-value ="0" type="System.Int32">
<generator class="identity" />
</id>

<property name="Text" column ="Note"/>

</class>


</hibernate-mapping>

ISession s = NHibernateSessionFactory.OpenSession();

ITransaction t = s.BeginTransaction();

User u = new User();
u.LastName="Wightman";
u.FirstName="Mike";


u.Notes = new List<Note>();

Note n=new Note();
n.Text="This is my note";


u.Notes.Add(n);

s.SaveOrUpdate(u);

t.Commit();

You probably have a not-null constraint on UserId in Notes ? When you specifiy the association in this way, hibernate first inserts the note and then updates the UserId. Check out the doc:

http://nhforge.org/doc/nh/en/index.html#example-parentchild

maybe just use inverse in the bag?

<bag generic="true" name="Notes" table="Notes" cascade="all" inverse="true">
<key column="UserID" not-null="true"/>
<one-to-many class ="NHiberTest.Objects.Note,NHiberTest.Objects"/>
</bag>

Inverse is just one part of the solution. You need a reference to User on Note.

I was under the impression that I did not need to refrence User from Note mapping unless I wanted the note to hold a back refrence to its owner.



back pointer example.
class
{
string name
Ilist<note> notes
}


class note
{
user owner <-back pointer
text
}

http://bchavez.bitarmory.com/archive/20 ... ibute.aspx



In the unidirectional case, the foreign key column in the child table doesn't map to a property in the child object; it is in the data model, but not the object model. Since it is unidirectional there is just a property in the parent object [that contains a collection of children]; not the child [the child object does not contain any information back to the parent]. In addition, the foreign key column [in the child table] has to be defined as nullable because Hibernate will first insert the child row (with a NULL foreign key) and then update it [the inserted row] later [with the parent's primary key].


I found this post explaining what I wish to accomplish and was a bit put put off by the statement "In addition, the foreign key column[in the child table] has to be defined as nullable because Hibernate will first insert the child row". From a DBA perspective this is a huge no-no and in most companies would not be accepted.

That's the way hibernate works. If you define a uni-directional association, the parent is the owner and does an update on the child.

This is an interesting architectural decision might I as what factors influenced this design.

Can't give you more details on that decission. You might ask the question on the developer list or nhusers group at google.