_____________________
|Bank                 |
|---------------------|
|id : Guid            |
|bankname : wchar(200)|
|_____________________|
                |
                |
               /|\
_____________________
|Constraint           |
|---------------------|
|id : Guid            |
|id_bank : Guid       |
|note : wchar(200)    |
|_____________________|

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0" namespace="BankManager" assembly="BankManager">
   <class name="Bank" table="Bank">
      <id name="Id" type="System.Guid" unsaved-value="00000000-0000-0000-0000-000000000000">
         <column name="id" sql-type="Guid" not-null="true" />
         <generator class="guid" />
      </id>
      <property name="BankName">
         <column name="bankname" length="200" not-null="true"/>
      </property>
      <list name="Constraints" table="Constraint">
         <key column="id_bank" />
         <index column="id" type="Guid"/>
         <one-to-many class="Constraint" />
      </list>
   </class>
</hibernate-mapping>

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0" namespace="BankManager" assembly="BankManager">
   <class name="Constraint" table="Constraint">
      <id name="Id" column="id" type="System.Guid" unsaved-value="00000000-0000-0000-0000-000000000000">
         <generator class="guid" />
      </id>
      <property name="Name">
         <column name="name" length="200" not-null="false"/>
      </property>
      <property name="Note">
         <column name="note" length="200" not-null="false"/>
      </property>
   </class>
</hibernate-mapping>

session.CreateCriteria(typeof(Bank)).List();

{"Could not cast the value in field id__ of type Guid to the Type Int32Type.  Please check to make sure that the mapping is correct and that your DataProvider supports this Data Type."}

{"Unable to cast object of type 'System.Guid' to type 'System.IConvertible'."}