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Get event state during event handling

28 Apr 2020 08:24 #8409 by KrisSik

Code you provided works:
UAFilterElements.SimpleAttribute(UAObjectTypeIds.AlarmConditionType, "/ActiveState"),

Thank you.

Best regards,

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27 Apr 2020 14:28 - 27 Apr 2020 14:28 #8406 by support
Yes, you are right, this is done using the Select clause.

The Active state is not present in all Events. In fact, not even in all Conditions. The conditions needs to be of the AlarmConditionType (see UA Spec 1.04 Part 9, chapter 5.8.2). In AlarmConditionType, there is ActiveState variable.

Assuming that this is what you are dealing with, you should be able to modify the example for Select clauses ( ) accordingly. Here is how it looks currently:
// This example shows how to select fields for event notifications.
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 =
            // Instantiate the client object and hook events
            var client = new EasyUAClient();
            client.EventNotification += client_EventNotification;
                new UAAttributeFieldCollection
                    // Select specific fields using standard operand symbols
                    // 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("Waiting for 5 seconds...");
            System.Threading.Thread.Sleep(5 * 1000);
        static void client_EventNotification(object sender, EasyUAEventNotificationEventArgs e)
            // Display the event
            if (e.EventData == null)
            Console.WriteLine("All fields:");
            foreach (KeyValuePair<UAAttributeField, ValueResult> pair in e.EventData.FieldResults)
                UAAttributeField attributeField = pair.Key;
                ValueResult valueResult = pair.Value;
                Console.WriteLine("  {0} -> {1}", attributeField, valueResult);
            // Extracting a specific field using a standard operand symbol
            Console.WriteLine("Source name: {0}", 
            // Extracting a specific field using an event type ID and a simple relative path
            Console.WriteLine("Message: {0}", 
                e.EventData.FieldResults[UAFilterElements.SimpleAttribute(UAObjectTypeIds.BaseEventType, "/Message")]);

and you would include something like
UAFilterElements.SimpleAttribute(UAObjectTypeIds.AlarmConditionType, "/ActiveState"),
(not tested)

Let me know if that works for you, please.

Best regards
Last edit: 27 Apr 2020 14:28 by support.
The following user(s) said Thank You: KrisSik

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27 Apr 2020 09:36 - 27 Apr 2020 09:43 #8403 by KrisSik

I am trying to get event's active/inactive state in the OpcClientOnEventNotification(object sender, EasyUAEventNotificationEventArgs e) event handler, but have no success in that, could you please help me?

I was expecting to see that attribute in the e.EventData.FieldResults, but that is not present in this dictionary. Maybe I need to configure the select clause while subscribing? For subscription I use SubscribeMultipleMonitoredItems method.

Best regards,
Last edit: 27 Apr 2020 09:43 by KrisSik.

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