Hi, I am trying to do standard bi-directional replication as follows. However, I get a NullReferenceException. This is a separate replication project. I did import the classes involved in the original project (such as Item, Category etc.) in this replication project. What am I doing wrong? (If I debug using VS, I can see that changedObjects does have all the changed objects; there seems to be some problem inside Replicate function) IObjectContainer local = Db4oFactory.OpenFile(@"G:\Work\School\MIS\VINMIS\Inventory\bin\Debug\vin.db4o"); IObjectContainer far = Db4oFactory.OpenFile(@"\\crs-lap\c$\vinmis\vin.db4o"); ; IReplicationSession replication = Replication.Begin(local, far); IObjectSet changedObjects = replication.ProviderA().ObjectsChangedSinceLastReplication(); while(changedObjects.HasNext()) replication.Replicate(changedObjects.Next()); // Exception!!! replication.Commit(); changedObjects = replication.ProviderB().ObjectsChangedSinceLastReplication(); while (changedObjects.HasNext()) replication.Replicate(changedObjects.Next()); replication.Commit(); Regards, Saurabh.