| Class | Description | |
|---|---|---|
 | DAItemChangedPayload<TValue> | An event payload for significant change in a subscribed OPC-DA item. |
| DAVtqPayload<TValue> | An event payload for OPC-DA data value, timestamp and quality. |
This namespace contains extension classes used to develop StreamInsight applications with OPC Data Access (OPC-DA).
Classes
Remarks
The event payload class for OPC Data Access is the DAItemChangedPayload<TValue>, where TValue is the type of the OPC values. This class contains an embedded DAVtqPayload<TValue> object, which contains the actual OPC value, timestamp, and quality. This object is always present; in case of errors, it contains default values.
In addition, there are Server and Item string properties, identifying the source of the event. For a single OPC observable, they always contain the same value, but they become useful once you start combining events from different OPC sources into one stream.
See Also