Hibernate version: 1.0.2

Name and version of the database you are using:ms sql server 2000
I use nhibernate as dao layer and it works well ,but I get a problem when I user sql profiler to watch sql server:when I get some data from a table (use query),nhibernate always executes some update statements after executing select. I dont know why ? I just map a class(ClassA) to a table ,this class reference another class(ClassB),such as:
class ClassA
{
private int id;
public int Id{get {return id;}set{id=value;}}
private ClassB refB;
public ClassB RefB
{
get{return refB;}
set{refB=value;}
}
....
}

class ClassB
{
....
}
and the map file is defined as following:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0">
<class name="ClassA" table="ea">
<id name="Id" column="Id">
<generator class="identity"/>
</id>
<many-to-one name="RefB" class="ClassB" cascade="none" >
<column name="B_code"/>
</many-to-one>
...
</hibernate-mapping >
help me,please!

That's how NHibernate works. If you use the default flushmode NHibernate will flush any changed objects in the session to the database before the select is performed so that the select will return the correct results. If you don't want the flush to occur change the flushmode for your session(s) but be aware that any query you run will be against the state of the database before the last time the data was flushed.

Cheers,

Symon.

but ,I did not change any data in classB before selected data from classA.
the map file for classB is:
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0">
<class name="ClassB" table="dmb_unit">
<id name="UnitCode" column="unit_code">
<generator class="assigned"/>
</id>
<property name="UnitName" column="unit_name" />
</class>
</hibernate-mapping>

by the way ,how to change the flushmode?

I'd pick up a copy of Hibernate in Action.
This behaviour is called transparent-transactional-write-behind.
You might consider using session.Evict on instances that you want to exclude from this behaviour. This detaches the instance from the first-level cache that is flushed and so changes to the object aren't synchronized with the DB.

the key point is that I have not change any data before select both classA and ClassB ,why does nhibernate determine the instance of ClassB had been changed?

See http://www.hibernate.org/116.html#A18.