For example I have 2 tables called ClassA and ClassB. 2 classes have connection many to many in the third table called ClassAB. ClassAB is very simple has some columns such as Id, ClassA_Id, ClassB_Id.
public class ClassA
{
public virtual string Name { get; set; }
private IList<ClassB> listB;
public virtual IList<ClassB> ListB
{
get
{
if (listB == null)
listB = new List<ClassB>();
return listB;
}
set { this.listB = value; }
}
public class ClassB
{
public virtual string Name { get; set; }
private IList<ClassA> listA;
public virtual IList<ClassA> ListA
{
get
{
if (listA == null)
listA = new List<ClassA>();
return listA;
}
set { this.listA = value; }
}
}
Mapping file for Class A will be:
<class name="ClassA" mutable="true" optimistic-lock="none" select-before-update="false" >
<cache usage="read-write"/>
<id name="Id" >
<column name="Id" not-null="true"/>
<generator class="guid.comb" />
</id>
<property name="Name" type="string" not-null="true"/>
<idbag name="ListB" lazy="true" table="ClassAB">
<collection-id column="Id" type="Guid">
<generator class="guid.comb" />
</collection-id>
<key column="ClassA_Id"/>
<many-to-many column="ClassB_Id" class="ClassB"/>
</idbag>
</class>
Mapping file for Class B will be same as Class A:
<class name="ClassB" mutable="true" optimistic-lock="none" select-before-update="false" >
<cache usage="read-write"/>
<id name="Id" >
<column name="Id" not-null="true"/>
<generator class="guid.comb" />
</id>
<property name="Name" type="string" not-null="true"/>
<idbag name="ListA" lazy="true" table="ClassAB" >
<collection-id column="Id" type="Guid">
<generator class="guid.comb" />
</collection-id>
<key column="ClassB_Id"/>
<many-to-many column="ClassA_Id" class="ClassA"/>
</idbag>
</class>
Insert a new ClassB and add a link to ClassA by inserting a record to the linked table
using (var trans = new Transaction())
{
var b = new ClassB();
b.Name = "class b";
SaveOrUpdate(b);
a.ListB.Add(b);
SaveOrUpdate(a);
trans.Commit();
}
Note: If I add an attribute inverse = true at idbag as <idbag name="ListB" lazy="true" table="ClassAB" inverse="true"> NHibernate won't insert into linked table ClassAB.
