Parent/child mapping file with only one database table

doggelito · **Joined:** Mon Jan 14, 2008 10:58 am **Posts:** 24

Hi everyone! :)

This is my mapping file as it is now:

Code:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
   <class name="Entities.Category, Entities" table="Categories">
      <id name="Id" column="CategoryID" type="int" unsaved-value="0">
         <generator class="identity" />
      </id>
      <property name="ParentId" column="ParentID" type="int"/>
      <property name="Name" column="CategoryName" type="String" length="50"/>
      <property name="CreateDate" type="DateTime"/>
      <property name="LastUpdatedDate" type="DateTime"/>
   </class>
</hibernate-mapping>

How should it be changed so ParentId has a relation to Id?

I have seen many examples with parent/child mappings but all of them has two tables and therefor also two classes.

karlchu · **Posted:** Mon Jan 14, 2008 11:41 am

With the given mapping, you are only mapping an INT column to an Int32 property; there is no relationship to speak of as far as NHibernate is concern. That said, NHibernate has no problem mapping the relationship that you desire: change the <property> to <many-to-one> like this:

Code:

<many-to-one name="Parent" column="ParentID" />

Also rename the ParentID property to "Parent" and change its type from "int" to "Category".

Read to the documentation for <many-to-one> to fully understand it:
http://www.hibernate.org/hib_docs/nhibe ... -manytoone

doggelito · **Joined:** Mon Jan 14, 2008 10:58 am **Posts:** 24

So thats how its done! Thanks Karl! :)