Syntax
| Visual Basic (Usage) |  Copy Code |
|---|---|
Dim instance As Session Dim nodesToRead As IList(Of HistoryReadValueId) Dim details As ReadProcessedDetails Dim timestampsToReturn As TimestampsToReturn Dim settings As RequestSettings Dim callback As AsyncCallback Dim userData As Object Dim value As IAsyncResult value = instance.BeginHistoryReadProcessed(nodesToRead, details, timestampsToReturn, settings, callback, userData) | |
| C# | |
|---|---|
public IAsyncResult BeginHistoryReadProcessed( IList<HistoryReadValueId> nodesToRead, ReadProcessedDetails details, TimestampsToReturn timestampsToReturn, RequestSettings settings, AsyncCallback callback, object userData ) | |
Parameters
- nodesToRead
- List of variable nodes to read processed data history from. Includes a continuation point to continue previous read requests.
- details
- Configuration parameters for the history read of processed data. Configuration parameters include - The start time of the requested time domain - The end time of the requested time domain - Time processing interval used to calculate one aggregated value from the raw values - The NodeId of the aggregate used for the calculation of the values
- timestampsToReturn
- Enumeration for the timestamps to return with the values. Possible values are
source,serverorboth. The optionneitheris invalid for history read. - settings
- The general settings for the request. If null, the default settings from the property #DefaultRequestSettings are used.
- callback
- The callback to use when the async call completes.
- userData
- The user data that is passed to the callback.
Return Value
An object which must be passed to the EndHistoryReadProcessed method.Remarks
This method is used to read processed historical values of one or more
nodes in an ordered sequence for the defined time domain.
Continuation points are used to continue the read of the ordered
sequence if not all data can be returned in one read or if the server
was not able to finish the processing before the timeout expired. The
returned number can be limited by the server and may be 0 if the
server was not able to finish one calculation before the service
timeout expired.
See #ReleaseHistoryContinuationPoints for cleaning up resources in the
server if read should not be continued with the returned continuation
point.
The processed values are calculated with the specified aggregate based
on the raw data in the history database. The server must use start
time, end time, and the resample interval to generate a sequence of
time intervals and then calculate an aggregate for each interval.
Requirements
Target Platforms: Windows 7/8/10, Windows Server 2003/2008/2012/2015, .NET4.x