The possibility of reference to an instance error:
1. The control does not exist.
2. Execution permissions are not enough. Add ASPNET and EVETRYOONE.
// below resons come from strong 2004
1. The ViewState object is Unll.
2, dateset empty.
3, the cause of SQL statement or DATEBASE causes DataReader empty.
4. Apply variables when declaring string variables.
5. There is no new initialization of the NEW.
6, the session object is empty.
