Leaving error situations aside, you still need to be careful when interpreting properties of XXXXEventArgs objects provided by the OPC observables. For precise description, study the corresponding topics in the “OPC Studio User's Guide” and the reference documentations. Here are some basic points to be aware of:

• In OPC Data Access, the EasyDAItemChangedEventArgs<T>.TypedVtq.TypedValue property does not contain valid data when the quality of the VTQ denotes a “Bad” quality.
• In OPC Alarms and Events, the EasyAENotificationEventArgs.EventData property does not contain valid data for in a notification that signifies a re-gained connection to the OPC server, or in a notification that indicates that a subscription refresh is complete.
• In OPC Unified Architecture, the EasyUADataChangeNotificationEventArgs<T>.TypedAttributeData.TypedValue property does not contain valid data when the status code of the attribute data denotes a “Bad” status.

When you use the pre-defined OPC Event Payload classes (described further below), the conversion code already takes these special cases into account, e.g. by filling in the payload fields with special values.