OPC Studio User's Guide and Reference
OpcLabs.EasyOpc.UA.Filtering Namespace
Inheritance Hierarchy
OpcLabs.EasyOpcUA Assembly : OpcLabs.EasyOpc.UA.Filtering Namespace
This namespace provides classes and interfaces that provide filtering capabilities in OPC Unified Architecture.
Classes
 ClassDescription
ClassAn operand consisting of an attribute of a node in a type, with optional relative path and alias.
ClassThe filter criteria (an operator and its operands).
ClassThe builder for content filter element.
ClassProvides an easy way to construct basic filter elements (literal, attribute, or a simple attribute), and elements with various operators.
ClassBase class for different types of filter operands.
ClassA collection of content filter operands.
ClassAn operand consisting of a literal value.
ClassAn operand consisting of an attribute of a node in a type, with optional simple relative path, and no alias.
ClassA collection of simple attribute operands.
Enumerations
 EnumerationDescription
EnumerationFilter operator to be evaluated.
Remarks

 

The UAEventFilter object (used for specifying the event filters) is probably the most complicated part of the OPC UA Alarms & Condition features. It has two main parts: Select clauses (contained in the SelectClauses property, of UAAttributeFieldCollection type), and a Where clause (contained in the WhereClause property, of UAContentFilterElement type). The Select clauses contain a collection of the attribute fields to return with each event in a notification. The Where clause contains the criteria limiting the notifications.

In order to make the creation of some event filters appear shorter in the code, a UAEventFilterBuilder class is provided. Instances of this builder can be implicitly converted to the event filter itself (hence you can create just the UAEventFilterBuilder objects, and use them at all places where the UAEventFilter object is expected). The builder contains a Where clause, and is a collection of Select clauses. You can therefore use the C# collection initializer to specify the Select clauses.

In COM (tools like VB6, Delphi etc.), creation of OPC UA Event Filters requires longer code. For related information, see http://kb.opclabs.com/Creating_an_OPC_UA_event_filter_in_COM .

 

See Also

Reference

OpcLabs.EasyOpcUA Assembly