Ilist Clients;
   clients = session.CreateQuery("from AcceesDonnee.BLL.Client").List(); ;

Ilist Clients;
   clients = session.CreateQuery("select c.Libelle from AcceesDonnee.BLL.Client c").List(); ;

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0">
  <class name="AcceesDonnee.BLL.Client, AcceesDonnee" table="Client">
    <!-- map the id field -->
    <id name="IdClient" column="IdClient" type="String" length="20">
      <generator class="assigned" />
    </id>
    <!-- Map properties I'd like to persist/fetch, assume column = propery name, and type is determined by reflection -->
    <property name="Libelle" not-null="false" type="String" length="30"/>
    <property name="RaisonSocial" not-null="false" type="String" length="30"/>
    <property name="CodePostal" not-null="false" type="String" length="30"/>
    <property name="Ville" not-null="false" type="String" length="30"/>
      <property name="Pays" not-null="false" type="String" length="30"/>
    <property name="Tel" not-null="false" type="String" length="30"/>
    <property name="Email" not-null="false" type="String" length="30"/>
    <property name="Comentaire" not-null="false" type="String" length="30"/>
    <property name="Type" not-null="false" type="String" length="30"/>
    <property name="Id_personel" not-null="false" type="String" length="30"/>
    <property name="Adresse" not-null="false" type="String" length="30"/>
    <bag name="Devis">
      <key column="IdClient" />
      <one-to-many
        class="AcceesDonnee.BLL.ClassDevisClient, AcceesDonnee" />
    </bag>
  </class>
</hibernate-mapping>