CRM 4.0 - Asignar una entidad a un usuario o team

apunte = (appointment)crmService.Retrieve(EntityName.appointment.ToString(), ((appointment)retrievedApunte.BusinessEntities[0]).activityid.Value, cs_apunte);

TargetOwnedAppointment tappointment = new TargetOwnedAppointment();
tappointment.EntityId = apunte.activityid.Value;

SecurityPrincipal sp = new SecurityPrincipal();
sp.PrincipalId = evento.ownerid.Value;
sp.Type = SecurityPrincipalType.User;

AssignRequest areq = new AssignRequest();

areq.Target = tappointment;
areq.Assignee = sp;

crmService.Execute(areq);