>This is the source code of my page.

Try adding the following call to StoreDataRow() after setting the current DataSet:

' Retrieve the previous Vxlve DataSet
Me.order.DataSet = CType(Session("Order"), Data.DataSet)
Me.order.StoreDataRow(Me.order.DataSet)

This populates the underlying DataRow used by the Entity object in this scenario.

Best Regards,