Hibernate version: 1.0.2.0.

Mapping documents:

Person.hbm.xml

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0">
<class name="NHibernateWeb.Person, NHibernateWeb" table="People">
<id name="ID" column="PersonID" type="Int32">
<generator class="assigned" />
</id>
<discriminator column="PersonType" type="String" />
<property name="FirstName" column="FirstName" />
<property name="LastName" column="LastName" />
<subclass name="NHibernateWeb.Professor, NHibernateWeb" discriminator-value="Professor">
<property name="Identifier" column="Identifier" type="String"/>
</subclass>
<subclass name="NHibernateWeb.Student, NHibernateWeb" discriminator-value="Student">
<property name="SSN" column="Identifier" type="String"/>
</subclass>
</class>
</hibernate-mapping>


Department.hbm.xml

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0" namespace="NHibernateWeb" assembly="NHibernateWeb" >
<class name="Department" table="Department">
<id name="ID" column="DeptID" type="Int32" unsaved-value="0">
<generator class="native" />
</id>
<property name="Name" column="DeptName" />
<set name="Classes" cascade="all">
<key column="DeptID" />
<one-to-many class="UniversityClass" />
</set>
<set name="Professors" table="DepartmentProfessor">
<key column="DeptID" />
<many-to-many class="Person" column="PersonID" />
</set>
</class>
</hibernate-mapping>


UniversityClass.hbm.xml

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0" namespace="NHibernateWeb" assembly="NHibernateWeb">
<class name="UniversityClass" table="UniversityClass">
<id name="ID" column="ClassID" type="Int32" unsaved-value="0">
<generator class="assigned" />
</id>
<property name="Name" column="ClassName" />
<property name="Number" column="ClassNumber" />
<property name="Syllabus" column="Syllabus" />
<property name="StartDate" column="StartDate" />
<many-to-one name="Department" class="Department" column="DeptID" not-null="true" />
</class>
</hibernate-mapping>


Code between sessionFactory.openSession() and session.close():

public System.Collections.IList getDepartments()
{
IList depts = null;

ISession session = factory.OpenSession();
ITransaction tx = session.BeginTransaction();
try
{
depts = session.CreateCriteria(typeof(Department)).List();
}
catch (Exception ex)
{
throw ex;
tx.Rollback();
// handle exception.
}
finally
{
session.Close();
}
return depts;
}






Full stack trace of any exception that occurs:

[InvalidCastException: Specified cast is not valid.]
NHibernate.Persister.GetSetHelper_NHibernateWeb_Department.SetPropertyValues(Object obj, Object[] values)

[MappingException: Invalid mapping information specified for type NHibernateWeb.Department, check your mapping file for property type mismatches]
NHibernateWeb.RegMgr.getDepartments() in c:\inetpub\wwwroot\nhibernateweb\regmgr.cs:40
NHibernateWeb.WebForm1.Page_Load(Object sender, EventArgs e) in c:\inetpub\wwwroot\nhibernateweb\webform1.aspx.cs:26
System.Web.UI.Control.OnLoad(EventArgs e)
System.Web.UI.Control.LoadRecursive()
System.Web.UI.Page.ProcessRequestMain()






Name and version of the database you are using:

SQL Server 2000




The generated SQL (show_sql=true):


I couldn't figured out how to do this.



Debug level Hibernate log excerpt:

I don't know what this is either.




I keep getting this error when I run my code, but I wrote this from an example site. I need a second pair of eyes on this cause the mappings look ok to me.

How does Your department class look like? Do You use generic lists? AFAIK, they are not yet supported by NHibernate.

Gert

Here is the Department class.


using System;
using System.Collections;

namespace NHibernateWeb
{
/// <summary>
/// Summary description for Department.
/// </summary>
public class Department
{
private int id;
private string name;
private IDictionary classes;
private IDictionary professors;

public int ID
{
get {return this.id;}
set {this.id = value;}
}

public string Name
{
get {return this.name;}
set {this.name = value;}
}

public IDictionary Classes
{
get {return this.classes;}
set {this.classes = value;}
}

public IDictionary Professors
{
get {return this.professors;}
set {this.professors = value;}
}

}
}


Sorry for my ignorance, but I am new to NHibernate. I am trying it out because I gave up my attempt to learn another popular O/R Mapper.

If You use Set mapping, the field (and property) should be declared as either IEsi.Collections.ISet or ICollection. <Set> is not assignable to IDictionary

Gert

That worked. I read the docs and I still don't quite understand why it worked, but it worked.

Thank you for your help.