dOPC Client Toolkit Help file
TdOPCEventFilter Class
dOPCAE.TdOPCEventFilter
C++
public: class TdOPCEventFilter : public TCollectionItem;
C#
public class TdOPCEventFilter : TCollectionItem;
Visual Basic
Public Class TdOPCEventFilter
Inherits TCollectionItem

dOPCAE

TdOPCEventFilter represents a single event subscription.

The client creates a subscription (filter) to receive only the desired event notifications from an OPC AE server. Each subscription between a client and server will have one filter only, but several criteria can be included in that filter. Clients can implement multiple filters, each with their own filter criteria. If no filter is established a default filter is created that is equivalent to "no filtering" (all event notifications will be sent). The primary reason for a filter is to reduce unnecessary communication overhead and to improve performance. Therefore the most important filtering criteria are for the severity and the process area. The server logically "ORs" together the list of values for a single filter (e.g. if two event categories are specified, event notifications for both categories will be received). The server logically "ANDs" together specified multiple filters (i.e. only events meeting all criteria will be selected). An example would be to specify both lowest severity and highest severity which then would result in the selection of events with severities lying between the two values. Servers may not support all the various filter criteria. If a filter criterion is specified that is not supported by the server, this filter criterion will be ignored.

TdOPCEventFilter Methods 
Description 
Refresh applies event filter changes. 
TdOPCEventFilter Properties 
Description 
Active is True if the filter is active, otherwise False
Areas contains an area filter, which means that only events of the specified areas will be reported. 
Categories contains a category filter, which means that only events of the specified categories will be reported. 
EventType contains the tdOPCEventtypes of the filter. 
Name 
Name contains the name of the filter. 
SeverityHigh contains a value indicating the highest severity of interest for the event. 
SeverityLow contains a value indicating the lowest severity of interest for the event. 
Sources contain a sources filter, which means that only events from these sources will be reported. 
Subscriptor contains the TdOPCEventSubscription for the filter. 
Tag 
Tag has no predefined meaning. 
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