but it keep generating the error: Object reference not set to an instance of an object.
Well, it happened because I didn't put 'New' while dimming the variable. But I just can't use the new keyword because it will create a new form and will not update the existing one. The scenario is like this:
1. frmDisplay is opened. User click a button to add new data
2. frmAddData is opened. User adds a few data and save it to database
3. Upon Close event of frmAddData, I want frmDisplay (or certain controls on it) to refresh, so new data will displayed.