public virtual void Save()
		{
			ISession session = NHibernateSessionManager.Instance.GetSession();
            if (!this.IsPersisted)
                session.Save(this);
            else
                session.SaveOrUpdateCopy(this);

			session.Flush();
		}

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
	<class name="Business.Product,Business" table="PRODUCT" lazy="true">

		<id name="Id" column="PRODUCTID" type="Int32">
      <generator class="native" />
		</id>

    
    <property name="Name" column="NAME" type="String"/>
    <property name="Weight" column="WEIGHT" type="Int32"/>
  </class>
</hibernate-mapping>

CREATE TABLE PRODUCT (
    PRODUCTID  INTEGER NOT NULL,
    NAME       VARCHAR( 50 ) NOT NULL,
    WEIGHT     INTEGER
);



/* Trigger: PRODUCT_BI */
CREATE TRIGGER PRODUCT_BI FOR PRODUCT
ACTIVE BEFORE INSERT POSITION  0 
as
begin
    new.productid = gen_id(gen_product_id, 1 );
end

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
	<class name="Business.Product,Business" table="PRODUCT" lazy="true">

      <id name="Id" type="Int32" column="PRODUCTID" unsaved-value="0">
          <generator class="sequence">
            <param name="sequence">GEN_PRODUCT_ID</param>
          </generator>
      </id>
    
    <property name="Name" column="NAME" type="String"/>
    <property name="Weight" column="WEIGHT" type="Int32"/>
  </class>
</hibernate-mapping>

CREATE GENERATOR GEN_PRODUCT_ID;

CREATE TABLE PRODUCT (
    PRODUCTID  INTEGER NOT NULL,
    NAME       VARCHAR( 50 ) NOT NULL,
    WEIGHT     INTEGER
);


/* Trigger: PRODUCT_BI */
CREATE TRIGGER PRODUCT_BI FOR PRODUCT
ACTIVE BEFORE INSERT POSITION  0 
as
begin
    new.productid = gen_id(gen_product_id, 1 );
end

CREATE GENERATOR HIBERNATE_SEQUENCE;

<generator class="identity"/>

<generator class="increment"/>

<generator class="assigned"/>

<generator class="native"/>

select gen_id(hibernate_sequence,  1  ) from RDB$DATABASE