<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
namespace="domain" assembly="Base">
  <class name="Delegation" table="delegation">
    <composite-id unsaved-value="none">
      <key-property name="ProjNo" column="projno" access="field.pascalcase-underscore" />
      <key-property name="Index" column="index" access="field.pascalcase-underscore" />
    </composite-id>
    <bag name="Voucheur" access="field.pascalcase-underscore" lazy="true" inverse="true" cascade="all">     
      <key>
        <column name="projmo"/>
        <column name="index"/>
      </key>     
      <one-to-many class="Voucheur" />
    </bag>
  </class>
</hibernate-mapping>

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
namespace="domain" assembly="Base">
  <class name="Voucheur" table="voucheur">
    <id name="VoucheurNo" column="voucheurno" access="field.pascalcase-underscore">
      <generator class="assigned" />
    </id>
    <many-to-one not-found="ignore" name="Einsatz" access="field.pascalcase-underscore">
      <column name="projnp"/>
      <column name="index"/>     
    </many-to-one>
  </class>
</hibernate-mapping>

public class Delegation
{
    private string _ProjNo;
    public virtual string ProjNo
    {
        get { return _ProjNo; }
        set { _ProjNo = value; }
    }

   private int? _Index;
    public virtual int? Index
    {
        get { return _Index; }
    }
       
    private IList<Voucheur> _Voucheurs = new List<Voucheur>();
    public virtual IList<Voucheur> Voucheurs
    {
        get { return _Voucheurs; }
    }
}

public class Voucheur
{
    protected int? _VoucheurNo;
    public virtual int? VoucheurNo
    {
        get { return _VoucheurNo; }
        set { _VoucheurNo = value; }
    }

    protected Delegation _Delegation;
    public virtual Delegation Delegation
    {
        get { return _Delegation; }
        set { _Delegation = value; }
    }
}