Thanks. I have been wondering if that might not be the best way. I
htink I read something different someplace to get me on the wrong way.
I have implemented the "dual one-to-many" strategy. But, I get an
error message saying that I, "Cannot insert the value NULL into
column". That column is the foreign key in the join table. Basically,
NH is not getting the id from the objects I am trying to connect to
the join table.
I am loathe to ask anyone to read much code, but I am clearly not
getting some important thing, so please be patient.
Here is what I have done:
<class ... student
<!-- all kinds of stuff that works except for this problem, id is
RefId, a uuid.hex -->
<bag name="schools">
<key column="SchoolInfoRefId"/>
<one-to-many class="AssemblyName.Models.StudentSchoolEnrollment,
AssemblyName" />
</bag>
</class>
<class ... school
<!-- all kinds of stuff that works except for this problem, id is
RefId, a uuid.hex -->
<bag name="students">
<key column="StudentPersonalRefId"/>
<one-to-many class="AssemblyName.Models.StudentSchoolEnrollment,
AssemblyName" />
</bag>
</bag>
</class>
<class ... StudentSchools ...
<!-- id and one property that is not controversial, but I haven't
built a separate test, id is RefId, a uuid.hex -->
<many-to-one class="AssemblyName.Models.Student, AssemblyName"
name="school" column="StudentPersonalRefId"/>
<many-to-one class="AssemblyName.Models.School, AssemblyName"
name="student" column="SchoolInfoRefId"/>
</class>
Classes:
In School: public virtual IList<StudentSchoolEnrollment>
students{get;set;} //initialized in the contructor
In Student: public virtual IList<StudentSchoolEnrollment> schools
{ get; set; } //initialized in the contructor
In StudentSchool:
public virtual School school {get; set;}
public virtual Student student { get; set; }
To test it, I wrap the following in a session:
Student newOne = new Student();
NameOfRecordType newName = new NameOfRecordType();
newName.FirstName="TQ";
newName.LastName="White";
newName.FullName="TQ White II";
newOne.Name = newName;
School newSchool = new School();
newSchool.LocalId = "School #1";
StudentSchoolEnrollment newEnrollment = new
StudentSchoolEnrollment();
newEnrollment.SchoolYear = "2010 and beyond";
newOne.schools.Add(newEnrollment);
newSchool.students.Add(newEnrollment);
session.Save(newSchool);
session.Save(newOne);
session.Save(newEnrollment);
If I remove the enrollment code (not removing xml), the school and
student are persisted correctly. If this were my bad, old sql days,
I'd be trying to figure out how to get private keys for school and
student, but am pretty sure NH is supposed to do that for me.
Thanks for your help.
tqii
On Mar 12, 9:22 am, Diego Mijelshon <[email protected]> wrote:
> You'll need to create an intermediate entity, and one-to-many relationships
> to it from the School and Student classes.
>
> Diego
>
>
>
> On Fri, Mar 12, 2010 at 12:08, tqwhite <[email protected]> wrote:
> > Is that a good way to title this? Do we have a better name for that
> > object that has both foreign keys?
>
> > Anyway, I am using a set of externally designed data types. Among them
> > is the connection between two of my entities, Schools and Students.
> > Each student can attend many schools. Each school has many students.
> > In addition, that period of attendance has a start and end date, etc.
>
> > I have constructed a mapping and it almost works. Two problems I need
> > help with:
>
> > 1) I am getting an error, "Cannot insert the value NULL into the
> > column RefId." It specifies the join table. RefId is the <id> column
> > for this intermediate. I bet that the problem is that NH doesn't
> > expect there to be an id on the joining table.
>
> > 2) I can't set said start and end dates because I can't find a way to
> > address that intermediate object.
>
> > I considered the idea that I should initialize that object in the
> > AddStudent() (and AddSchool()) method but the needed id keys don't
> > exist yet.
>
> > I spent last night poring over my brand, new copy of NHibernate in
> > Action (I LOVE THAT BOOK!), but can't find any advice.
>
> > Help! Please.
>
> > thanks,
> > tqii
>
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