nhibernate many-to-many mapping three tables. jumpstart - nhibernate

Question

I am trying to get this solved but can't so far. all kind of errors.
These are my db tables
Person (personID, name, age)
Role (roleID, roleName)
PersonRoles(personRolesID, personID, roleID)
this is my domain class
public Person
{
public virtual Roles RolesForThisPerson {get;set;}
public virtual string Name {get;set;}
public virtual int Age {get;set;}
}
public Roles
{
public virtual IList<string> RoleList {get;set;}
}
I am totally lost on how to approach this. I am so confused about sets, bags, lists... i don't even know where to start.
Anybody can give me a little push here?
thanks

Answer 1

Let's keep the DB schema as it is and adjust the C# domain classes first:
public class Person
{
public virtual string Name {get;set;}
public virtual int Age {get;set;}
public virtual IList<Role> RolesForThisPerson {get;set;}
}
public class Role
{
public virtual string RoleName { get; set; }
}
Now basic mapping for these two entities into defined tables:
<class name="Person" table="Person" lazy="true">
<id name="ID" column="personID">
<generator class="native" />
</id>
<property name="Name" not-null="true" />
<property name="Age" not-null="true" />
<!-- placeholder for roles -->
</class>
<class name="Role" table="Role" lazy="true">
<id name="ID" column="roleID">
<generator class="native" />
</id>
<property name="RoleName" not-null="true" />
</class>
And now we can use the <idbag> mapping and extend the Person class mapping this way:
<idbag name="RolesForThisPerson" batch-size="25" table="PersonRoles"
inverse="true" lazy="true" cascade="none" >
<collection-id column="personRolesID" type="System.Int32" >
<generator class="native" />
</collection-id>
<key column="personID" />
<many-to-many class="Role" column="roleID" />
</idbag>
The <idbag> can profit from the fact, that even the pair table has its own identifier. Cascade is set to none, expecting that roles are in the system, and users are only assigned to them (removed from). Attribute batch-size will effect how many SELECT statements will be executed when fetching the lazy roles collection.