Does nHibernate concurrency approach supports for mulitple aplicatin accessing same database?
Example: Say there are two applications accessing same database. Application 1 and 2 reads the same data. Application 1 does some modification on it and invokde ISession.Update() so that same changes will be reflected into the database. Now application 2 contains stale data, application 2 performs modificaition and tried to update the same using ISession.Update() but update should fail because the data contained by Applicaiton 2 is stale.
Now please let me know whethere nHibernate supported optimistic concurrency mechanism works only if there is single application accessing the database or not?

I have gone through the document but still I am not able to figure out how to use concurrency in multiple ISession?
Is there any setting needs to be done in mapping file?

Hi.

I'm not sure, but i think the only way to do that is implementing the "Equals" method using all your attributes to compare. Try that. If i'm not wrong the nhibernate uses the "Equals" to compare them before saving it.

Try it and say if it works.

My problem is "If there are 2 applications accessing same data,
-Say app 1 and 2 accessed same object i.e. Obj_A
-App1 does some modification on it and calls ISession.Update
-Then App2 does some modification on it and calls ISession.Update on it, now nHibernate should throw an exception as it is a dirty object but it doesn't work in my case.

Thanks,
Deepak

Am I missing something in mapping file?
nHibernate optimistic approach for "Many sessions with automatic versioning" is not working for me even though for each data request applicaiotn is creating new ISession object :(


<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0">
<class name="MisysHealthCare.BusinessEntities.Patient,MisysHealthCare.BusinessEntities" table="Patient" lazy="true" optimistic-lock="all" dynamic-update="true">

<id name="Id" column="ID" type="Int32" unsaved-value="0">
<generator class="identity"/>
</id>
<bag name="PrescriptionList" cascade="all" inverse="true" lazy="true" >
<key column="PatientID" />
<one-to-many class="MisysHealthCare.BusinessEntities.Prescription,MisysHealthCare.BusinessEntities" />
<!--<loader query-ref="PrescriptionList"/>-->
</bag>
<property column="FirstName" type="String" name="FirstName" length="50" />
<property column="MiddleName" type="String" name="MiddleName" length="50" />
<property column="LastName" type="String" name="LastName" not-null="true" length="50" />
<property column="DOB" type="System.DateTime" name="Dob" />
<property column="Gender" type="MisysHealthCare.BusinessEntities.GenderEnumType,MisysHealthCare.BusinessEntities" name="Gender" not-null="false" length="1" />
<property column="SSN" type="String" name="Ssn" length="11" />
<many-to-one name="PrimaryCarePhysicianid" column="PrimaryCarePhysicianID" class="MisysHealthCare.BusinessEntities.Doctor,MisysHealthCare.BusinessEntities" />
<many-to-one name="HomeAddressid" column="HomeAddressID" class="MisysHealthCare.BusinessEntities.Address,MisysHealthCare.BusinessEntities" />
<property column="HomePhone" type="String" name="HomePhone" length="50" />
<many-to-one name="WorkAddressid" column="WorkAddressID" class="MisysHealthCare.BusinessEntities.Address,MisysHealthCare.BusinessEntities" />
<property column="WorkPhone" type="String" name="WorkPhone" length="50" />
<property column="TimeStamp" type="System.Byte[]" name="TimeStamp" length="50" /><!--update="false" insert="false"/>-->
</hibernate-mapping>

Try adding a <version> tag to your mapping. You can find information on it in the documentation.

Cheers,

Symon.