NHibernate问题，集合列的读取。
目前有两个表，职员表和部门表。其中职员表中的部门ID是集合列，如何把当前职员的部门ID显示出来呢。
我的代码如下。
映射文件及XML文件：
职员表XML文件
<?xml   version= "1.0 "   encoding= "utf-8 "   ?>
<hibernate-mapping   xmlns= "urn:nhibernate-mapping-2.2 "   namespace= "Domain.Admin "   assembly= "Domain ">
    <class   name= "Staff "   table= "PB_STAFF "   proxy= "Staff ">
        <cache   usage= "read-write "   />
        <id   name= "LoginId "   column= "PB_LOGIN_ID "   type= "String "   length= "20 ">
            <generator   class= "assigned "/>
        </id>
        <property   name= "Password "   column= "PB_PASSWORD "   type= "String "   not-null= "true "   length= "40 "   />
        <property   name= "Code "   column= "PB_CODE "   type= "String "   length= "40 "   />
        <property   name= "Name "   column= "PB_NAME "   type= "String "   not-null= "true "   length= "40 "   />
        <property   name= "Sex "   column= "PB_SEX "   type= "Nullables.NHibernate.NullableInt32Type,   Nullables.NHibernate "   />
        <property   name= "Disabled "   column= "PB_DISABLED "   type= "Int32 "   not-null= "true "   />
        <property   name= "OrderId "   column= "PB_ORDER_ID "   type= "Int32 "   not-null= "true "   />
        <many-to-one   name= "Department "   column= "PB_DEPARTMENT_ID "   class= "Department "   />
        <set   name= "Roles "   table= "PB_STAFF_ROLE "   lazy= "true ">
            <cache   usage= "read-write "   />
            <key   column= "PB_LOGIN_ID "   />
            <many-to-many   class= "Role "   column= "PB_ROLE_ID "   outer-join= "false "   />
        </set>
        <set   name= "ModuleRightsGrant "   table= "PB_STAFF_MODULE_RIGHT_GRANT "   lazy= "true ">
            <cache   usage= "read-write "   />
            <key   column= "PB_LOGIN_ID "   />
            <many-to-many   class= "ModuleRight "   column= "PB_RIGHT_ID "   outer-join= "false "   />
        </set>
        <set   name= "ModuleRightsDeny "   table= "PB_STAFF_MODULE_RIGHT_DENY "   lazy= "true ">