This synchronous function reads the attribute values and timestamps from the history database for the specified time domain for an item.
If the current values for the attributes are desired, startTime shall be set to "NOW" and endTime shall be null (Nothing).
This function is intended to be used to retrieve attributes that have changed to correlate the values of these attributes with the values of their data. For example, the recalibration of a sensor may have required the normal maximum and minimum attributes to be changed.
Overload List
| Overload | Description |
|---|---|
| ReadAttribute(OPCHDAtime,OPCHDAtime,Int32,Int32[],OPCHDAattribute[],Int32[]) | This synchronous function reads the attribute values and timestamps from the history database for the specified time domain for an item. If the current values for the attributes are desired, startTime shall be set to "NOW" and endTime shall be null (Nothing). |
| ReadAttribute(Int32,OPCHDAtime,OPCHDAtime,Int32,Int32[],Int32,Int32[]) | This asynchronous function reads the attribute values and timestamps from the history database for the specified time domain for an item. This function is intended to be used to retrieve attributes that have changed to correlate the values of these attributes with the values of their data. For example, the recalibration of a sensor may have required the normal maximum and minimum attributes to be changed. The results are returned via the client's ReadAttributeComplete event handler. |
Requirements
Target Platforms: Windows 7/8/10, Windows Server 2008/2012/2016, .NET 4.x