OPC Studio User's Guide and Reference
Examples - OPC UA Alarms&Conditions - Specify Select clauses in an event filter
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.NET

// This example shows how to select fields for event notifications.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-CSharp .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

using System;
using System.Collections.Generic;
using OpcLabs.BaseLib.OperationModel;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.AddressSpace.Standard;
using OpcLabs.EasyOpc.UA.AlarmsAndConditions;
using OpcLabs.EasyOpc.UA.Filtering;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples.AlarmsAndConditions
{
    class SelectClauses
    {
        public static void Main1()
        {
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer";

            // Instantiate the client object and hook events.
            var client = new EasyUAClient();
            client.EventNotification += client_EventNotification;

            Console.WriteLine("Subscribing...");
            client.SubscribeEvent(
                endpointDescriptor,
                UAObjectIds.Server,
                1000,
                new UAAttributeFieldCollection
                {
                    // Select specific fields using standard operand symbols.
                    UABaseEventObject.Operands.NodeId,
                    UABaseEventObject.Operands.SourceNode,
                    UABaseEventObject.Operands.SourceName,
                    UABaseEventObject.Operands.Time,

                    // Select specific fields using an event type ID and a simple relative path.
                    UAFilterElements.SimpleAttribute(UAObjectTypeIds.BaseEventType, "/Message"),
                    UAFilterElements.SimpleAttribute(UAObjectTypeIds.BaseEventType, "/Severity")
                });

            Console.WriteLine("Processing event notifications for 30 seconds...");
            System.Threading.Thread.Sleep(30 * 1000);

            Console.WriteLine("Unsubscribing...");
            client.UnsubscribeAllMonitoredItems();

            Console.WriteLine("Waiting for 5 seconds...");
            System.Threading.Thread.Sleep(5 * 1000);

            Console.WriteLine("Finished.");
        }

        static void client_EventNotification(object sender, EasyUAEventNotificationEventArgs e)
        {
            Console.WriteLine();

            // Display the event.
            if (e.EventData is null)
            {
                Console.WriteLine(e);
                return;
            }
            Console.WriteLine("All fields:");
            foreach (KeyValuePair<UAAttributeField, ValueResult> pair in e.EventData.FieldResults)
            {
                UAAttributeField attributeField = pair.Key;
                ValueResult valueResult = pair.Value;
                Console.WriteLine($"  {attributeField} -> {valueResult}");
            }

            // Extracting a specific field using a standard operand symbol.
            Console.WriteLine($"Source name: {e.EventData.FieldResults[UABaseEventObject.Operands.SourceName]}");

            // Extracting a specific field using an event type ID and a simple relative path.
            Console.WriteLine(
                $"Message: {e.EventData.FieldResults[UAFilterElements.SimpleAttribute(UAObjectTypeIds.BaseEventType, "/Message")]}");
        }
    }
}

COM

// This example shows how to select fields for event notifications.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in Object Pascal (Delphi) on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-OP .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

type
  THelperMethods17 = class
    class function ObjectTypeIds_BaseEventType: _UANodeId; static;
    class function UABaseEventObject_Operands_NodeId: _UASimpleAttributeOperand;
    class function UAFilterElements_SimpleAttribute(TypeId: _UANodeId; simpleRelativeBrowsePathString: string): _UASimpleAttributeOperand; static;
    class function UABaseEventObject_Operands_SourceName: _UASimpleAttributeOperand; static;
    class function UABaseEventObject_Operands_Time: _UASimpleAttributeOperand; static;
    class function UABaseEventObject_Operands_SourceNode: _UASimpleAttributeOperand; static;
    class function UABaseEventObject_Operands_Message: _UASimpleAttributeOperand; static;
    class function UABaseEventObject_Operands_Severity: _UASimpleAttributeOperand; static;
  end;

type
  TClientEventHandlers17 = class
    procedure Client_EventNotification(
      ASender: TObject;
      sender: OleVariant;
      const eventArgs: _EasyUAEventNotificationEventArgs);
  end;

procedure TClientEventHandlers17.Client_EventNotification(
  ASender: TObject;
  sender: OleVariant;
  const eventArgs: _EasyUAEventNotificationEventArgs);
var
  AttributeField: OleVariant;
  Count: Cardinal;
  Element: OleVariant;
  EntryEnumerator: IEnumVARIANT;
  ValueResult: OleVariant;
begin
  WriteLn;

  // Display the event
  if eventArgs.EventData = nil then
  begin
    WriteLn(eventArgs.ToString);
    Exit;
  end;

  WriteLn('All fields:');

  EntryEnumerator := eventArgs.EventData.FieldResults.GetEnumerator;
  while (EntryEnumerator.Next(1, Element, Count) = S_OK) do
  begin
    AttributeField := IUnknown(Element.Key) as _UAAttributeField;
    ValueResult := IUnknown(Element.Value) as _ValueResult;
    WriteLn(' ', AttributeField.ToString, ' -> ', ValueResult.ToString);
  end;

  // Extracting specific fields using an event type ID and a simple relative path
  WriteLn('Source name: ', eventArgs.EventData.FieldResults.Item[THelperMethods17.UABaseEventObject_Operands_SourceName.ToUAAttributeField].ToString);
  WriteLn('Message: ', eventArgs.EventData.FieldResults.Item[THelperMethods17.UABaseEventObject_Operands_Message.ToUAAttributeField].ToString);
end;

class procedure SelectClauses.Main;
const
  UAObjectIds_Server = 'nsu=http://opcfoundation.org/UA/;i=2253';
var
  Arguments: OleVariant;
  Client: TEasyUAClient;
  ClientEventHandlers: TClientEventHandlers17;
  EndpointDescriptor: string;
  EventFilter: _UAEventFilter;
  MonitoredItemArguments: _EasyUAMonitoredItemArguments;
  MonitoringParameters: _UAMonitoringParameters;
  SelectClauses: UAAttributeFieldCollection;
begin
  EndpointDescriptor := 'opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer';

  // Instantiate the client object and hook events
  Client := TEasyUAClient.Create(nil);
  ClientEventHandlers := TClientEventHandlers17.Create;
  Client.OnEventNotification := ClientEventHandlers.Client_EventNotification;

  WriteLn('Subscribing...');

  SelectClauses := CoUAAttributeFieldCollection.Create;
  // Select specific fields using an event type ID and a simple relative path
  SelectClauses.Add(THelperMethods17.UABaseEventObject_Operands_NodeId.ToUAAttributeField);
  SelectClauses.Add(THelperMethods17.UABaseEventObject_Operands_SourceNode.ToUAAttributeField);
  SelectClauses.Add(THelperMethods17.UABaseEventObject_Operands_SourceName.ToUAAttributeField);
  SelectClauses.Add(THelperMethods17.UABaseEventObject_Operands_Time.ToUAAttributeField);
  SelectClauses.Add(THelperMethods17.UABaseEventObject_Operands_Message.ToUAAttributeField);
  SelectClauses.Add(THelperMethods17.UABaseEventObject_Operands_Severity.ToUAAttributeField);

  EventFilter := CoUAEventFilter.Create;
  EventFilter.SelectClauses := SelectClauses;

  MonitoringParameters := CoUAMonitoringParameters.Create;
  MonitoringParameters.SamplingInterval := 1000;
  MonitoringParameters.EventFilter := EventFilter;
  MonitoringParameters.QueueSize := 1000;

  MonitoredItemArguments := CoEasyUAMonitoredItemArguments.Create;
  MonitoredItemArguments.EndpointDescriptor.UrlString := EndpointDescriptor;
  MonitoredItemArguments.NodeDescriptor.NodeId.StandardName := 'Server';
  MonitoredItemArguments.MonitoringParameters := MonitoringParameters;
  //MonitoredItemArguments.SubscriptionParameters.PublishingInterval := 0;
  MonitoredItemArguments.AttributeId := UAAttributeId_EventNotifier;

  Arguments := VarArrayCreate([0, 0], varVariant);
  Arguments[0] := MonitoredItemArguments;

  Client.SubscribeMultipleMonitoredItems(Arguments);

  WriteLn('Processing event notifications for 30 seconds...');
  PumpSleep(30*1000);

  WriteLn('Unsubscribing...');
  Client.UnsubscribeAllMonitoredItems;

  WriteLn('Waiting for 5 seconds...');
  Sleep(5*1000);

  WriteLn('Finished.');
  VarClear(Arguments);
  FreeAndNil(Client);
  FreeAndNil(ClientEventHandlers);
end;


class function THelperMethods17.ObjectTypeIds_BaseEventType: _UANodeId;
  var NodeId: _UANodeId;
  begin
    NodeId := CoUANodeId.Create;
    NodeId.StandardName := 'BaseEventType';
    Result := NodeId;
  end;

class function THelperMethods17.UAFilterElements_SimpleAttribute(TypeId: _UANodeId; simpleRelativeBrowsePathString: string): _UASimpleAttributeOperand;
var
  BrowsePathParser: _UABrowsePathParser;
  Operand: _UASimpleAttributeOperand;
begin
  BrowsePathParser := CoUABrowsePathParser.Create;
  Operand := CoUASimpleAttributeOperand.Create;
  Operand.TypeId.NodeId := TypeId;
  Operand.QualifiedNames := BrowsePathParser.ParseRelative(simpleRelativeBrowsePathString).ToUAQualifiedNameCollection;
  Result := Operand;
end;

class function THelperMethods17.UABaseEventObject_Operands_NodeId: _UASimpleAttributeOperand;
var
  Operand: _UASimpleAttributeOperand;
begin
  Operand := CoUASimpleAttributeOperand.Create;
  Operand.TypeId.NodeId.StandardName := 'BaseEventType';
  Operand.AttributeId := UAAttributeId_NodeId;
  Result := Operand;
end;

class function THelperMethods17.UABaseEventObject_Operands_SourceNode: _UASimpleAttributeOperand;
begin
  Result := UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, '/SourceNode');
end;

class function THelperMethods17.UABaseEventObject_Operands_SourceName: _UASimpleAttributeOperand;
begin
  Result := UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, '/SourceName');
end;

class function THelperMethods17.UABaseEventObject_Operands_Time: _UASimpleAttributeOperand;
begin
  Result := UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, '/Time');
end;

class function THelperMethods17.UABaseEventObject_Operands_Message: _UASimpleAttributeOperand;
begin
  Result := UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, '/Message');
end;

class function THelperMethods17.UABaseEventObject_Operands_Severity: _UASimpleAttributeOperand;
begin
  Result := UAFilterElements_SimpleAttribute(ObjectTypeIds_BaseEventType, '/Severity');
end;

Python

# This example shows how to select fields for event notifications.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python .
# Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
# a commercial license in order to use Online Forums, and we reply to every post.
# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc
import time

# Import .NET namespaces.
from OpcLabs.EasyOpc.UA import *
from OpcLabs.EasyOpc.UA.AddressSpace.Standard import *
from OpcLabs.EasyOpc.UA.AlarmsAndConditions import *
from OpcLabs.EasyOpc.UA.Filtering import *
from OpcLabs.EasyOpc.UA.OperationModel import *


def eventNotification(sender, eventArgs):
    print()

    # Display the event.
    if eventArgs.EventData is None:
        print(eventArgs)
        return
    print('All fields:')
    for pair in eventArgs.EventData.FieldResults:
        attributeField = pair.Key
        valueResult = pair.Value
        print('  ', attributeField, ' -> ', valueResult, sep='')

    # Extracting a specific field using a standard operand symbol.
    print('Source name: ',
          eventArgs.EventData.FieldResults.get_Item(UAAttributeField(UABaseEventObject.Operands.SourceName)),
          sep='')

    # Extracting a specific field using an event type ID and a simple relative path.
    print('Message: ',
          eventArgs.EventData.FieldResults.get_Item(UAAttributeField(
              UAFilterElements.SimpleAttribute(UANodeDescriptor(UAObjectTypeIds.BaseEventType), '/Message'))),
          sep='')


# Define which server we will work with.
endpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer')

# Instantiate the client object and hook events.
client = EasyUAClient()
client.EventNotification += eventNotification

print('Subscribing...')
attributeFieldCollection = UAAttributeFieldCollection([
    # Select specific fields using standard operand symbols.
    UAAttributeField(UABaseEventObject.Operands.NodeId),
    UAAttributeField(UABaseEventObject.Operands.SourceNode),
    UAAttributeField(UABaseEventObject.Operands.SourceName),
    UAAttributeField(UABaseEventObject.Operands.Time),

    # Select specific fields using an event type ID and a simple relative path.
    UAAttributeField(UAFilterElements.SimpleAttribute(UANodeDescriptor(UAObjectTypeIds.BaseEventType), "/Message")),
    UAAttributeField(UAFilterElements.SimpleAttribute(UANodeDescriptor(UAObjectTypeIds.BaseEventType), "/Severity"))
    ])
IEasyUAClientExtension.SubscribeEvent(
    client,
    endpointDescriptor,
    UANodeDescriptor(UAObjectIds.Server),
    1000,
    UAEventFilter(attributeFieldCollection))

print('Processing event notifications for 30 seconds...')
time.sleep(30)

print()
print('Unsubscribing...')
client.UnsubscribeAllMonitoredItems()

print('Waiting for 5 seconds...')
time.sleep(5)

print('Finished.')

 

See Also

Concepts

Examples - Client OPC Alarms&Events