I have solved this problem.
I had registered this plugin in update message, then changed RegisterFile.crmregister
MessageName="Disassociate"
and PrimaryEntityName=""
also changed the default constructor of the my plugin class.
base.RegisteredEvents.Add(new Tuple<int, string, string, Action<LocalPluginContext>>(10, "Disassociate", "", new Action<LocalPluginContext>(ExecutePreValidateProjectUpdate)));
Hope this will help someone facing same problem.