c# - Why one-to-many does not work as expected in NHibernate? -

i have simple situation , don't have clue why isn't working.

this schema:

**[item]** id (pk) symbol  **[item_version]** id (pk) item_id (fk->item) symbol 

these mappings:

item.hbm.xml

<class name="core.model.entities.item, core.model" table="item" lazy="false">     <id name="id" column="id" type="long">         <generator class="native" />     </id>     <property name="symbol" column="symbol"/>      <bag name="itemversions" lazy="false" table="item_version" inverse="true" cascade="save-update">         <key column="item_id" />         <one-to-many class="core.model.entities.itemversion, core.model"/>     </bag> </class> 

*item_version.hbm.xml*

<class name="core.model.entities.itemversion, core.model" table="item_version" lazy="false">     <id name="id" column="id" type="long">         <generator class="native" />     </id>      <many-to-one name="item" class="core.model.entities.item, core.model" column="item_id" cascade="save-update"/>     <property name="symbol" column="symbol"/>     </class> 

these classes:

item.cs

public class item : entity<iitemdao> {    private long id;    virtual public long id    {        { return this.id; }        set { this.id = value; }    }    private string symbol;    virtual public string symbol    {        { return this.symbol; }        set { this.symbol = value; }    }    private ilist<itemversion> item_versions = new list<itemversion>();    virtual public ilist<itemversion> itemversions    {        { return this.item_versions; }        set { this.item_versions = value; }    } } 

itemversion.cs

public class itemversion : entity<iitemversiondao> {     private long id;     virtual public long id     {          { return this.id; }          set { this.id = value; }     }     private item item = null;     virtual public item item     {          { return this.item; }          set { this.item = value; }     }     private long item_id = 0;     virtual public long itemid     {          { return this.item_id; }          set { this.item_id = value; }     }     private string symbol;     virtual public string symbol     {          { return this.symbol; }          set { this.symbol = value; }     } } 

and code...

item item = new item(); item.name = "test";  itemversion v = new itemversion(); v.symbol = "test version"; item.itemversions.add(v);  item.dao.save(tmp); 

... not work. inserts item , throws exception while inserting item_version row, item_version.item_id cannot null. item_id property isn't automatically set nhibernate in itemversion object. why cascade="save-update" , inverse="true" not work in case?

when set manually, adding code:

v.item = item; 

and call save, works fine, not except nhibernate - calling

item.itemversions.add(v); 

should sufficient.

am doing wrong or imposible? in advance answers :)

you have set v.item because itemversions inverse. means "other side" (the many-to-one) in charge of maintaining relationship.

this standard practice; make easier use add method item:

public void additemversion(itemversion itemversion) {     itemversions.add(itemversion);     itemversion.item = this; }