OPC Studio User's Guide and Reference
DataChangeNotification Event (IEasyUAClient)
Example 



OpcLabs.EasyOpcUA Assembly > OpcLabs.EasyOpc.UA Namespace > IEasyUAClient Interface : DataChangeNotification Event
Raised for every significant change in a subscribed OPC monitored item.
Syntax
'Declaration
 

Event DataChangeNotification As EasyUADataChangeNotificationEventHandler
'Usage
 

Dim instance As IEasyUAClient
Dim handler As EasyUADataChangeNotificationEventHandler
 
AddHandler instance.DataChangeNotification, handler
event EasyUADataChangeNotificationEventHandler DataChangeNotification
event EasyUADataChangeNotificationEventHandler^ DataChangeNotification
Event Data

The event handler receives an argument of type EasyUADataChangeNotificationEventArgs containing data related to this event. The following EasyUADataChangeNotificationEventArgs properties provide information specific to this event.

PropertyDescription
ArgumentsHolds arguments that were used to subscribe to a monitored item in an OPC-UA server.  
AttributeDataAttribute data: the value of an attribute, together with status code and timestamps.  
DiagnosticsDiagnostics information (such as warnings) assembled during the operation. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs)
DiagnosticsCountCount of diagnostic information elements assembled during the operation. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs)
DiagnosticsSummaryTextual summary of diagnostics information, one message per line. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs)
ErrorIdGets or sets the error ID of the error. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs)
ErrorMessageGets or sets a message that describes the current exception. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs)
ErrorMessageBriefThe first line of the error message. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs)
ExceptionGets the current exception. Contains null reference when no exception. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs)
NormalizedDiagnosticsA normalized OpcLabs.BaseLib.OperationModel.OperationEventArgs.Diagnostics collection. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs)
NormalizedExceptionA normalized OpcLabs.BaseLib.OperationModel.OperationEventArgs.Exception object, or null if there was no error. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs)
StatusInfoStatus information corresponding to the contents of the event arguments.  
SucceededGets indication whether the operation has succeeded. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs)
Example
// This example shows how to subscribe to changes of a single monitored item and display the value of the item with each
// change.
//
// 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 OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples._EasyUAClient
{
    partial class SubscribeDataChange
    {
        public static void Overload1()
        {
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";
            // or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            // or "https://opcua.demo-this.com:51212/UA/SampleServer/"

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

            Console.WriteLine("Subscribing...");
            client.SubscribeDataChange(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853", 1000);

            Console.WriteLine("Processing data change events for 20 seconds...");
            System.Threading.Thread.Sleep(20 * 1000);

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

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

            Console.WriteLine("Finished.");
        }

        static void client_DataChangeNotification(object sender, EasyUADataChangeNotificationEventArgs e)
        {
            // Display value.
            if (e.Succeeded)
                Console.WriteLine($"Value: {e.AttributeData.Value}");
            else
                Console.WriteLine($"*** Failure: {e.ErrorMessageBrief}");
        }
    }
}
# This example shows how to subscribe to changes of a single monitored item and display the value of the item with each
# change.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in PowerShell on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-PowerShell .
# 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.

#requires -Version 5.1
using namespace OpcLabs.EasyOpc.UA

# The path below assumes that the current directory is [ProductDir]/Examples-NET/PowerShell/Windows .
Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcUA.dll"
Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcUAComponents.dll"

[UAEndpointDescriptor]$endpointDescriptor =
    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
# or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
# or "https://opcua.demo-this.com:51212/UA/SampleServer/"

# Instantiate the client object.
$client = New-Object EasyUAClient

# Data change notification handler
Register-ObjectEvent -InputObject $client -EventName DataChangeNotification -Action { 
    # Display value.
    if ($EventArgs.Succeeded) {
        Write-Host "Value: $($EventArgs.AttributeData.Value)"
    }
    else {
        Write-Host "*** Failure: $($EventArgs.ErrorMessageBrief)"
    }
}

Write-Host "Subscribing..."
$client.SubscribeDataChange($endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853", 1000)

Write-Host "Processing data change events for 20 seconds..."
$stopwatch =  [System.Diagnostics.Stopwatch]::StartNew() 
while ($stopwatch.Elapsed.TotalSeconds -lt 20) {    
    Start-Sleep -Seconds 1
}

Write-Host "Unsubscribing..."
$client.UnsubscribeAllMonitoredItems()

Write-Host "Waiting for 5 seconds..."
Start-Sleep -Seconds 5

Write-Host "Finished."

' This example shows how to subscribe to changes of a single monitored item and display the value of the item with each change.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET .
' 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.

Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace _EasyUAClient
    Friend Class SubscribeDataChange
        Public Shared Sub Overload1()

            ' Define which server we will work with.
            Dim endpointDescriptor As UAEndpointDescriptor =
                    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
            ' or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            ' or "https://opcua.demo-this.com:51212/UA/SampleServer/"

            ' Instantiate the client object and hook events
            Dim client = New EasyUAClient()
            AddHandler client.DataChangeNotification, AddressOf client_DataChangeNotification

            Console.WriteLine("Subscribing...")
            client.SubscribeDataChange(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853", 1000)

            Console.WriteLine("Processing monitored item changed events for 10 seconds...")
            Threading.Thread.Sleep(10 * 1000)

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

            Console.WriteLine("Waiting for 5 seconds...")
            Threading.Thread.Sleep(5 * 1000)
        End Sub

        Private Shared Sub client_DataChangeNotification(ByVal sender As Object, ByVal e As EasyUADataChangeNotificationEventArgs)
            ' Display value
            If e.Succeeded Then
                Console.WriteLine("Value: {0}", e.AttributeData.Value)
            Else
                Console.WriteLine("*** Failure: {0}", e.ErrorMessageBrief)
            End If
        End Sub
    End Class
End Namespace

# This example shows how to subscribe to changes of a single monitored item and display the value of the item with each
# change.
#
# 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.OperationModel import *


def dataChangeNotification(sender, e):
    # Display value.
    if e.Succeeded:
        print('Value: ', e.AttributeData.Value, sep='')
    else:
        print('*** Failure: ', e.ErrorMessageBrief, sep='')


endpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:51210/UA/SampleServer')
# or 'http://opcua.demo-this.com:51211/UA/SampleServer' (currently not supported)
# or 'https://opcua.demo-this.com:51212/UA/SampleServer/'

# Instantiate the client object and hook events.
client = EasyUAClient()
client.DataChangeNotification += dataChangeNotification

print('Subscribing...')
IEasyUAClientExtension.SubscribeDataChange(client,
    endpointDescriptor,
    UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10853'),
    1000)

print('Processing data change events for 20 seconds...')
time.sleep(20)

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

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

print('Finished.')

// This example shows how to subscribe to changes of multiple monitored items and display the value of the monitored item with 
// each change.
//
// 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 OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples._EasyUAClient
{
    partial class SubscribeMultipleMonitoredItems
    {
        public static void Main1()
        {
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";
            // or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            // or "https://opcua.demo-this.com:51212/UA/SampleServer/"

            // Instantiate the client object and hook events.
            var client = new EasyUAClient();
            client.DataChangeNotification += client_DataChangeNotification_Main1;

            Console.WriteLine("Subscribing...");
            client.SubscribeMultipleMonitoredItems(new[]
                {
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor, 
                        "nsu=http://test.org/UA/Data/ ;i=10845", 1000),
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor, 
                        "nsu=http://test.org/UA/Data/ ;i=10853", 1000),
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor, 
                        "nsu=http://test.org/UA/Data/ ;i=10855", 1000)
                });

            Console.WriteLine("Processing monitored item changed events for 10 seconds...");
            System.Threading.Thread.Sleep(10 * 1000);

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

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

            Console.WriteLine("Finished.");
        }

        static void client_DataChangeNotification_Main1(object sender, EasyUADataChangeNotificationEventArgs e)
        {
            // Display value.
            if (e.Succeeded)
                Console.WriteLine($"{e.Arguments.NodeDescriptor}: {e.AttributeData.Value}");
            else
                Console.WriteLine($"{e.Arguments.NodeDescriptor} *** Failure: {e.ErrorMessageBrief}");
        }
    }
}
# This example shows how to subscribe to changes of multiple monitored items and display the value of the monitored item with 
# each change.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in PowerShell on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-PowerShell .
# 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.

#requires -Version 5.1
using namespace OpcLabs.EasyOpc.UA
using namespace OpcLabs.EasyOpc.UA.OperationModel

# The path below assumes that the current directory is [ProductDir]/Examples-NET/PowerShell/Windows .
Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcUA.dll"
Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcUAComponents.dll"

[UAEndpointDescriptor]$endpointDescriptor =
    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
# or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
# or "https://opcua.demo-this.com:51212/UA/SampleServer/"

# Instantiate the client object.
$client = New-Object EasyUAClient

# Data change notification handler
Register-ObjectEvent -InputObject $client -EventName DataChangeNotification -Action { 
    # Display value.
    if ($EventArgs.Succeeded) {
        Write-Host "$($EventArgs.Arguments.NodeDescriptor): $($EventArgs.AttributeData.Value)"
    }
    else {
        Write-Host "$($EventArgs.Arguments.NodeDescriptor) *** Failure: $($EventArgs.ErrorMessageBrief)"
    }
}

Write-Host "Subscribing..."
$handleArray = $client.SubscribeMultipleMonitoredItems(@(
    (New-Object UAMonitoredItemArguments(
        (New-Object UAAttributeArguments($endpointDescriptor, [UANodeDescriptor]"nsu=http://test.org/UA/Data/ ;i=10845")), 
        1000)),
    (New-Object UAMonitoredItemArguments(
        (New-Object UAAttributeArguments($endpointDescriptor, [UANodeDescriptor]"nsu=http://test.org/UA/Data/ ;i=10853")), 
        1000)),
    (New-Object UAMonitoredItemArguments(
        (New-Object UAAttributeArguments($endpointDescriptor, [UANodeDescriptor]"nsu=http://test.org/UA/Data/ ;i=10855")),
        1000))
    ))

Write-Host
Write-Host "Processing monitored item changed events for 10 seconds..."
$stopwatch =  [System.Diagnostics.Stopwatch]::StartNew() 
while ($stopwatch.Elapsed.TotalSeconds -lt 10) {    
    Start-Sleep -Seconds 1
}

Write-Host "Unsubscribing..."
$client.UnsubscribeAllMonitoredItems()

Write-Host "Waiting for 5 seconds..."
Start-Sleep -Seconds 5

Write-Host "Finished."

' This example shows how to subscribe to changes of multiple monitored items and display the value of the monitored item with 
' each change.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET .
' 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.

Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace _EasyUAClient
    Partial Friend Class SubscribeMultipleMonitoredItems
        Public Shared Sub Main1()

            ' Define which server we will work with.
            Dim endpointDescriptor As UAEndpointDescriptor =
                    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
            ' or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            ' or "https://opcua.demo-this.com:51212/UA/SampleServer/"

            ' Instantiate the client object and hook events
            Dim client = New EasyUAClient()
            AddHandler client.DataChangeNotification, AddressOf client_DataChangeNotification

            Console.WriteLine("Subscribing...")
            client.SubscribeMultipleMonitoredItems(New EasyUAMonitoredItemArguments() _
                {
                    New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10845", 1000),
                    New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853", 1000),
                    New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10855", 1000)
                }
             )

            Console.WriteLine("Processing monitored item changed events for 10 seconds...")
            Threading.Thread.Sleep(10 * 1000)

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

            Console.WriteLine("Waiting for 5 seconds...")
            Threading.Thread.Sleep(5 * 1000)
        End Sub

        Private Shared Sub client_DataChangeNotification(ByVal sender As Object, ByVal e As EasyUADataChangeNotificationEventArgs)
            ' Display value
            If e.Succeeded Then
                Console.WriteLine($"{e.Arguments.NodeDescriptor}: {e.AttributeData.Value}")
            Else
                Console.WriteLine($"{e.Arguments.NodeDescriptor} *** Failure: {e.ErrorMessageBrief}")
            End If
        End Sub
    End Class
End Namespace

# This example shows how to subscribe to changes of multiple monitored items and display the value of the monitored item
# with each change.
#
# 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.OperationModel import *


def dataChangeNotification(sender, e):
    # Display value.
    if e.Succeeded:
        print(e.Arguments.NodeDescriptor, ': ', e.AttributeData.Value, sep='')
    else:
        print(e.Arguments.NodeDescriptor, ' *** Failure: ', e.ErrorMessageBrief, sep='')


endpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:51210/UA/SampleServer')
# or 'http://opcua.demo-this.com:51211/UA/SampleServer' (currently not supported)
# or 'https://opcua.demo-this.com:51212/UA/SampleServer/'

# Instantiate the client object and hook events.
client = EasyUAClient()
client.DataChangeNotification += dataChangeNotification

print('Subscribing...')
client.SubscribeMultipleMonitoredItems([
    EasyUAMonitoredItemArguments(
        None,
        endpointDescriptor,
        UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10845'),
        UAMonitoringParameters(1000)),
    EasyUAMonitoredItemArguments(
        None,
        endpointDescriptor,
        UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10853'),
        UAMonitoringParameters(1000)),
    EasyUAMonitoredItemArguments(
        None,
        endpointDescriptor,
        UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10855'),
        UAMonitoringParameters(1000)),
    ])

print('Processing data change events for 10 seconds...')
time.sleep(10)

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

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

print('Finished.')

// This example shows how to subscribe to changes of multiple monitored items
// and display each change, identifying the different subscriptions by an
// integer.
//
// 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.Threading;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples._EasyUAClient
{
    partial class SubscribeMultipleMonitoredItems
    {
        public static void StateAsInteger()
        {
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";
            // or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            // or "https://opcua.demo-this.com:51212/UA/SampleServer/"
            
            // Instantiate the client object and hook events.
            var client = new EasyUAClient();
            client.DataChangeNotification += ClientOnDataChangeNotification_StateAsInteger;

            Console.WriteLine("Subscribing...");
            int[] handleArray = client.SubscribeMultipleMonitoredItems(new[]
                {
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor, 
                        "nsu=http://test.org/UA/Data/ ;i=10845", 1000)
                        {State = 1},    // An integer we have chosen to identify the subscription
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor, 
                        "nsu=http://test.org/UA/Data/ ;i=10853", 1000)
                        {State = 2},    // An integer we have chosen to identify the subscription
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor, 
                        "nsu=http://test.org/UA/Data/ ;i=10855", 1000)
                        {State = 3}     // An integer we have chosen to identify the subscription
                });

            for (int i = 0; i < handleArray.Length; i++)
                Console.WriteLine($"handleArray[{i}]: {handleArray[i]}");

            Console.WriteLine("Processing monitored item changed events for 10 seconds...");
            Thread.Sleep(10 * 1000);

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

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

            Console.WriteLine("Finished.");
        }

        static void ClientOnDataChangeNotification_StateAsInteger(object sender, EasyUADataChangeNotificationEventArgs eventArgs)
        {
            // Obtain the integer state we have passed in.
            var stateAsInteger = (int) eventArgs.Arguments.State;

            // Display the data.
            if (eventArgs.Succeeded)
                Console.WriteLine($"{stateAsInteger}: {eventArgs.AttributeData}");
            else
                Console.WriteLine($"{stateAsInteger} *** Failure: {eventArgs.ErrorMessageBrief}");
        }
    }
}
# This example shows how to subscribe to changes of multiple monitored items
# and display each change, identifying the different subscriptions by an
# integer.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in PowerShell on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-PowerShell .
# 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.

#requires -Version 5.1
using namespace OpcLabs.EasyOpc.UA
using namespace OpcLabs.EasyOpc.UA.OperationModel

# The path below assumes that the current directory is [ProductDir]/Examples-NET/PowerShell/Windows .
Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcUA.dll"
Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcUAComponents.dll"

[UAEndpointDescriptor]$endpointDescriptor =
    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
# or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
# or "https://opcua.demo-this.com:51212/UA/SampleServer/"

# Instantiate the client object.
$client = New-Object EasyUAClient

# Data change notification handler
Register-ObjectEvent -InputObject $client -EventName DataChangeNotification -Action { 
    # Obtain the integer state we have passed in.
    [int]$stateAsInteger = $EventArgs.Arguments.State

    # Display the data.
    if ($EventArgs.Succeeded) {
        Write-Host "$($stateAsinteger): $($EventArgs.AttributeData)"
    }
    else {
        Write-Host "$($stateAsinteger) *** Failure: $($EventArgs.ErrorMessageBrief)"
    }
}

Write-Host "Subscribing..."
$handleArray = $client.SubscribeMultipleMonitoredItems(@(
    (New-Object UAMonitoredItemArguments(
        (New-Object UAAttributeArguments($endpointDescriptor, [UANodeDescriptor]"nsu=http://test.org/UA/Data/ ;i=10845")), 
        1000) -Property @{State = 1}), # An integer we have chosen to identify the subscription
    (New-Object UAMonitoredItemArguments(
        (New-Object UAAttributeArguments($endpointDescriptor, [UANodeDescriptor]"nsu=http://test.org/UA/Data/ ;i=10853")), 
        1000) -Property @{State = 2}), # An integer we have chosen to identify the subscription
    (New-Object UAMonitoredItemArguments(
        (New-Object UAAttributeArguments($endpointDescriptor, [UANodeDescriptor]"nsu=http://test.org/UA/Data/ ;i=10855")),
        1000) -Property @{State = 3}) # An integer we have chosen to identify the subscription
    ))

for ($i = 0; $i -lt $handleArray.Length; $i++) {
    Write-Host "handleArray[$($i)]: $($handleArray[$i])"
}

Write-Host
Write-Host "Processing monitored item changed events for 10 seconds..."
$stopwatch =  [System.Diagnostics.Stopwatch]::StartNew() 
while ($stopwatch.Elapsed.TotalSeconds -lt 10) {    
    Start-Sleep -Seconds 1
}

Write-Host "Unsubscribing..."
$client.UnsubscribeAllMonitoredItems()

Write-Host "Waiting for 5 seconds..."
Start-Sleep -Seconds 5

Write-Host "Finished."

' This example shows how to subscribe to changes of multiple monitored items
' and display each change, identifying the different subscriptions by an
' integer.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET .
' 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.

Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace _EasyUAClient
    Partial Friend Class SubscribeMultipleMonitoredItems
        Public Shared Sub StateAsInteger()

            ' Define which server we will work with.
            Dim endpointDescriptor As UAEndpointDescriptor =
                    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
            ' or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            ' or "https://opcua.demo-this.com:51212/UA/SampleServer/"

            ' Instantiate the client object and hook events
            Dim client = New EasyUAClient()
            AddHandler client.DataChangeNotification, AddressOf ClientOnDataChangeNotification_StateAsInteger

            Console.WriteLine("Subscribing...")
            Dim handleArray() As Integer = client.SubscribeMultipleMonitoredItems(New EasyUAMonitoredItemArguments() _
                { _
                    New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor, _
                        "nsu=http://test.org/UA/Data/ ;i=10845", 1000) _
                         With {.State = 1}, _
                    New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor, _
                        "nsu=http://test.org/UA/Data/ ;i=10853", 1000) _
                         With {.State = 2}, _
                    New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor, _
                        "nsu=http://test.org/UA/Data/ ;i=10855", 1000) _
                        With {.State = 3} _
                } _
             ) ' An integer we have chosen to identify the subscription

            For i As Integer = 0 To handleArray.Length - 1
                Console.WriteLine("handleArray[{0}]: {1}", i, handleArray(i))
            Next i

            Console.WriteLine("Processing monitored item changed events for 10 seconds...")
            Threading.Thread.Sleep(10 * 1000)

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

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

            Console.WriteLine("Finished.")
        End Sub

        Private Shared Sub ClientOnDataChangeNotification_StateAsInteger(ByVal sender As Object, ByVal eventArgs As EasyUADataChangeNotificationEventArgs)
            ' Obtain the integer state we have passed in.
            Dim stateAsInteger As Integer = CInt(eventArgs.Arguments.State)

            ' Display the data
            If eventArgs.Succeeded Then
                Console.WriteLine("{0}: {1}", stateAsInteger, eventArgs.AttributeData)
            Else
                Console.WriteLine("{0} *** Failure: {1}", stateAsInteger, eventArgs.ErrorMessageBrief)
            End If
        End Sub
    End Class
End Namespace

REM This example shows how to subscribe to changes of multiple monitored items
REM and display each change, identifying the different subscriptions by an
REM integer.
REM
REM Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
REM OPC client and subscriber examples in Visual Basic on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VB .
REM Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
REM a commercial license in order to use Online Forums, and we reply to every post.

' The client object, with events
'Public WithEvents Client6 As EasyUAClient

Public Sub SubscribeMultipleMonitoredItems_StateAsInteger_Command_Click()
    OutputText = ""

    Set Client6 = New EasyUAClient

    OutputText = OutputText & "Subscribing..." & vbCrLf
    Dim MonitoringParameters As New UAMonitoringParameters
    MonitoringParameters.SamplingInterval = 1000
    
    Dim MonitoredItemArguments1 As New EasyUAMonitoredItemArguments
    MonitoredItemArguments1.endpointDescriptor.UrlString = "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
    MonitoredItemArguments1.nodeDescriptor.NodeId.expandedText = "nsu=http://test.org/UA/Data/ ;i=10845"
    Set MonitoredItemArguments1.MonitoringParameters = MonitoringParameters
    MonitoredItemArguments1.SetState 1 ' An integer we have chosen to identify the subscription
    
    Dim MonitoredItemArguments2 As New EasyUAMonitoredItemArguments
    MonitoredItemArguments2.endpointDescriptor.UrlString = "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
    MonitoredItemArguments2.nodeDescriptor.NodeId.expandedText = "nsu=http://test.org/UA/Data/ ;i=10853"
    Set MonitoredItemArguments2.MonitoringParameters = MonitoringParameters
    MonitoredItemArguments2.SetState 2 ' An integer we have chosen to identify the subscription
    
    Dim MonitoredItemArguments3 As New EasyUAMonitoredItemArguments
    MonitoredItemArguments3.endpointDescriptor.UrlString = "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
    MonitoredItemArguments3.nodeDescriptor.NodeId.expandedText = "nsu=http://test.org/UA/Data/ ;i=10855"
    Set MonitoredItemArguments3.MonitoringParameters = MonitoringParameters
    MonitoredItemArguments3.SetState 3 ' An integer we have chosen to identify the subscription
    
    Dim arguments(2) As Variant
    Set arguments(0) = MonitoredItemArguments1
    Set arguments(1) = MonitoredItemArguments2
    Set arguments(2) = MonitoredItemArguments3
    Dim handleArray As Variant
    handleArray = Client6.SubscribeMultipleMonitoredItems(arguments)

    Dim i As Long: For i = LBound(handleArray) To UBound(handleArray)
        OutputText = OutputText & "handleArray(" & i & "): " & handleArray(i) & vbCrLf
    Next

    OutputText = OutputText & "Processing monitored item changed events for 10 seconds..." & vbCrLf
    Pause 10000

    OutputText = OutputText & "Unsubscribing..." & vbCrLf
    Call Client6.UnsubscribeAllMonitoredItems

    OutputText = OutputText & "Waiting for 5 seconds..." & vbCrLf
    Pause 5000

    Set Client2 = Nothing
    OutputText = OutputText & "Finished." & vbCrLf
End Sub

Public Sub Client6_DataChangeNotification(ByVal sender As Variant, ByVal eventArgs As EasyUADataChangeNotificationEventArgs)
    ' Obtain the integer state we have passed in.
    Dim stateAsInteger As Integer: stateAsInteger = eventArgs.arguments.State
    If eventArgs.Succeeded Then
        OutputText = OutputText & stateAsInteger & ": " & eventArgs.AttributeData & vbCrLf
    Else
        OutputText = OutputText & stateAsInteger & " *** Failure: " & eventArgs.ErrorMessageBrief & vbCrLf
    End If
End Sub
# This example shows how to subscribe to changes of multiple monitored items
# and display each change, identifying the different subscriptions by an
# integer.
#
# 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.OperationModel import *


def dataChangeNotification(sender, eventArgs):
    # Obtain the integer state we have passed in.
    stateAsInteger = int(eventArgs.Arguments.State)
    # Display value.
    if eventArgs.Succeeded:
        print(stateAsInteger, ': ', eventArgs.AttributeData.Value, sep='')
    else:
        print(stateAsInteger, ' *** Failure: ', eventArgs.ErrorMessageBrief, sep='')


endpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:51210/UA/SampleServer')
# or 'http://opcua.demo-this.com:51211/UA/SampleServer' (currently not supported)
# or 'https://opcua.demo-this.com:51212/UA/SampleServer/'

# Instantiate the client object and hook events.
client = EasyUAClient()
client.DataChangeNotification += dataChangeNotification

print('Subscribing...')
monitoredItemArguments1 = EasyUAMonitoredItemArguments(
    None,
    endpointDescriptor,
    UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10845'),
    UAMonitoringParameters(1000))
monitoredItemArguments1.State = 1   # an integer we have chosen to identify the subscription
monitoredItemArguments2 = EasyUAMonitoredItemArguments(
    None,
    endpointDescriptor,
    UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10853'),
    UAMonitoringParameters(1000))
monitoredItemArguments2.State = 2   # an integer we have chosen to identify the subscription
monitoredItemArguments3 = EasyUAMonitoredItemArguments(
    None,
    endpointDescriptor,
    UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10855'),
    UAMonitoringParameters(1000))
monitoredItemArguments3.State = 3   # an integer we have chosen to identify the subscription

client.SubscribeMultipleMonitoredItems([
    monitoredItemArguments1,
    monitoredItemArguments2,
    monitoredItemArguments3,
    ])

print('Processing data change events for 10 seconds...')
time.sleep(10)

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

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

print('Finished.')

// This example shows how to subscribe to changes of multiple monitored items
// and display each change, identifying the different subscriptions by an
// object.
//
// 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.Threading;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples._EasyUAClient
{
    partial class SubscribeMultipleMonitoredItems
    {
        class CustomObject
        {
            public CustomObject(string name)
            {
                Name = name;
            }

            public string Name { get; }
        }
        

        public static void StateAsObject()
        {
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";
            // or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            // or "https://opcua.demo-this.com:51212/UA/SampleServer/"

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

            Console.WriteLine("Subscribing...");
            int[] handleArray = client.SubscribeMultipleMonitoredItems(new[]
                {
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor, 
                        "nsu=http://test.org/UA/Data/ ;i=10845", 1000)
                        {State = new CustomObject("First")},    // A custom object that corresponds to the subscription
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor, 
                        "nsu=http://test.org/UA/Data/ ;i=10853", 1000)
                        {State = new CustomObject("Second")},    // A custom object that corresponds to the subscription
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor, 
                        "nsu=http://test.org/UA/Data/ ;i=10855", 1000)
                        {State = new CustomObject("Third")},    // A custom object that corresponds to the subscription
                });

            for (int i = 0; i < handleArray.Length; i++)
                Console.WriteLine($"handleArray[{i}]: {handleArray[i]}");

            Console.WriteLine("Processing monitored item changed events for 10 seconds...");
            Thread.Sleep(10 * 1000);

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

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

            Console.WriteLine("Finished.");
        }

        static void ClientOnDataChangeNotification_StateAsObject(object sender, EasyUADataChangeNotificationEventArgs eventArgs)
        {
            // Obtain the custom object we have passed in.
            var stateAsObject = (CustomObject) eventArgs.Arguments.State;

            // Display the data
            if (eventArgs.Succeeded)
                Console.WriteLine($"{stateAsObject.Name}: {eventArgs.AttributeData}");
            else
                Console.WriteLine($"{stateAsObject.Name} *** Failure: {eventArgs.ErrorMessageBrief}");
        }
    }
}
' This example shows how to subscribe to changes of multiple monitored items
' and display each change, identifying the different subscriptions by an
' object.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET .
' 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.

Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace _EasyUAClient
    Partial Friend Class SubscribeMultipleMonitoredItems
        Class CustomObject
            Public Sub New(ByVal name As String)
                _Name = name
            End Sub
            Public ReadOnly Property Name As String
                Get
                    Return _Name
                End Get
            End Property
            Private ReadOnly _Name As String
        End Class

        Public Shared Sub StateAsObject()

            ' Define which server we will work with.
            Dim endpointDescriptor As UAEndpointDescriptor =
                    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
            ' or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            ' or "https://opcua.demo-this.com:51212/UA/SampleServer/"

            ' Instantiate the client object and hook events
            Dim client = New EasyUAClient()
            AddHandler client.DataChangeNotification, AddressOf ClientOnDataChangeNotification_StateAsObject

            Console.WriteLine("Subscribing...")
            Dim handleArray() As Integer = client.SubscribeMultipleMonitoredItems(New EasyUAMonitoredItemArguments() _
                { _
                    New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor, _
                        "nsu=http://test.org/UA/Data/ ;i=10845", 1000) _
                         With {.State = New CustomObject("First")}, _
                    New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor, _
                        "nsu=http://test.org/UA/Data/ ;i=10853", 1000) _
                         With {.State = New CustomObject("Second")}, _
                    New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor, _
                        "nsu=http://test.org/UA/Data/ ;i=10855", 1000) _
                        With {.State = New CustomObject("Third")} _
                } _
            ) ' A custom object that corresponds to the subscription

            For i As Integer = 0 To handleArray.Length - 1
                Console.WriteLine("handleArray[{0}]: {1}", i, handleArray(i))
            Next i

            Console.WriteLine("Processing monitored item changed events for 10 seconds...")
            Threading.Thread.Sleep(10 * 1000)

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

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

            Console.WriteLine("Finished.")
        End Sub

        Private Shared Sub ClientOnDataChangeNotification_StateAsObject(ByVal sender As Object, ByVal eventArgs As EasyUADataChangeNotificationEventArgs)
            ' Obtain the custom object we have passed in.
            Dim stateAsObject As CustomObject = CType(eventArgs.Arguments.State, CustomObject)

            ' Display the data
            If eventArgs.Succeeded Then
                Console.WriteLine("{0}: {1}", stateAsObject.Name, eventArgs.AttributeData)
            Else
                Console.WriteLine("{0} *** Failure: {1}", stateAsObject.Name, eventArgs.ErrorMessageBrief)
            End If
        End Sub
    End Class
End Namespace

# This example shows how to subscribe to changes of multiple monitored items
# and display each change, identifying the different subscriptions by an
# object.
#
# 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.OperationModel import *


class CustomObject(object):
    def __init__(self, name):
        self.name = name


def dataChangeNotification(sender, eventArgs):
    # Obtain the custom object we have passed in.
    stateAsObject = eventArgs.Arguments.State
    # Display value.
    if eventArgs.Succeeded:
        print(stateAsObject.name, ': ', eventArgs.AttributeData.Value, sep='')
    else:
        print(stateAsObject.name, ' *** Failure: ', eventArgs.ErrorMessageBrief, sep='')


endpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:51210/UA/SampleServer')
# or 'http://opcua.demo-this.com:51211/UA/SampleServer' (currently not supported)
# or 'https://opcua.demo-this.com:51212/UA/SampleServer/'

# Instantiate the client object and hook events.
client = EasyUAClient()
client.DataChangeNotification += dataChangeNotification

print('Subscribing...')
monitoredItemArguments1 = EasyUAMonitoredItemArguments(
    None,
    endpointDescriptor,
    UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10845'),
    UAMonitoringParameters(1000))
monitoredItemArguments1.State = CustomObject('First')    # a custom object that corresponds to the subscription
monitoredItemArguments2 = EasyUAMonitoredItemArguments(
    None,
    endpointDescriptor,
    UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10853'),
    UAMonitoringParameters(1000))
monitoredItemArguments2.State = CustomObject('Second')    # a custom object that corresponds to the subscription
monitoredItemArguments3 = EasyUAMonitoredItemArguments(
    None,
    endpointDescriptor,
    UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10855'),
    UAMonitoringParameters(1000))
monitoredItemArguments3.State = CustomObject('Third')    # a custom object that corresponds to the subscription

client.SubscribeMultipleMonitoredItems([
    monitoredItemArguments1,
    monitoredItemArguments2,
    monitoredItemArguments3,
    ])

print('Processing data change events for 10 seconds...')
time.sleep(10)

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

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

print('Finished.')

// This example shows how to subscribe to changes of all data variables under a specified object in OPC UA address space.
//
// 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.Linq;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.AddressSpace;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples._EasyUAClient
{
    partial class SubscribeMultipleMonitoredItems
    {
        public static void AllInObject()
        {
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";
            // or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            // or "https://opcua.demo-this.com:51212/UA/SampleServer/"
            
            // Instantiate the client object and hook events
            var client = new EasyUAClient();
            client.DataChangeNotification += client_DataChangeNotification_AllInObject;

            // Obtain variables under "Scalar" node
            Console.WriteLine("Browsing...");
            UANodeElementCollection nodeElementCollection;
            try
            {
                nodeElementCollection = client.BrowseDataVariables(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;ns=2;i=10787");
            }
            catch (UAException uaException)
            {
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message);
                return;
            }

            // Create array with monitored item arguments
            EasyUAMonitoredItemArguments[] monitoredItemArgumentsArray = nodeElementCollection
                .Select(element => new EasyUAMonitoredItemArguments(null, endpointDescriptor, element))
                .ToArray();

            Console.WriteLine("Subscribing...");
            client.SubscribeMultipleMonitoredItems(monitoredItemArgumentsArray);

            Console.WriteLine("Processing monitored item changed events for 20 seconds...");
            System.Threading.Thread.Sleep(20 * 1000);

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

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

        static void client_DataChangeNotification_AllInObject(object sender, EasyUADataChangeNotificationEventArgs e)
        {
            // Display value
            if (e.Succeeded)
                Console.WriteLine("{0}: {1}", e.Arguments.NodeDescriptor, e.AttributeData.Value);
            else
                Console.WriteLine("{0} *** Failure: {1}", e.Arguments.NodeDescriptor, e.ErrorMessageBrief);
        }
    }
}
' This example shows how to subscribe to changes of all data variables under a specified object in OPC UA address space.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET .
' 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.

Imports System.Linq
Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.AddressSpace
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace _EasyUAClient
    Partial Friend Class SubscribeMultipleMonitoredItems
        Public Shared Sub AllInObject()

            ' Define which server we will work with.
            Dim endpointDescriptor As UAEndpointDescriptor =
                "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
            ' or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            ' or "https://opcua.demo-this.com:51212/UA/SampleServer/"

            ' Instantiate the client object and hook events
            Dim client = New EasyUAClient()
            AddHandler client.DataChangeNotification, AddressOf client_DataChangeNotification_AllInObject

            ' Obtain variables under "Scalar" node
            Console.WriteLine("Subscribing...")
            Dim nodeElementCollection As UANodeElementCollection
            Try
                nodeElementCollection = client.BrowseDataVariables(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;ns=2;i=10787")
            Catch uaException As UAException
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException.Message)
                Exit Sub
            End Try

            ' Create array with monitored item arguments

            Dim monitoredItemArgumentsArray() As EasyUAMonitoredItemArguments = nodeElementCollection.Select(Function(element) New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor, element)).ToArray()

            Console.WriteLine("Subscribing...")
            client.SubscribeMultipleMonitoredItems(monitoredItemArgumentsArray)

            Console.WriteLine("Processing monitored item changed events for 20 seconds...")
            Threading.Thread.Sleep(20 * 1000)

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

            Console.WriteLine("Waiting for 5 seconds...")
            Threading.Thread.Sleep(5 * 1000)
        End Sub

        Private Shared Sub client_DataChangeNotification_AllInObject(ByVal sender As Object, ByVal e As EasyUADataChangeNotificationEventArgs)
            ' Display value
            If e.Succeeded Then
                Console.WriteLine("{0}: {1}", e.Arguments.NodeDescriptor, e.AttributeData.Value)
            Else
                Console.WriteLine("{0} *** Failure: {1}", e.Arguments.NodeDescriptor, e.ErrorMessageBrief)
            End If
        End Sub
    End Class
End Namespace

# This example shows how to subscribe to changes of multiple monitored items and display the value of the monitored item
# with each change.
#
# 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.OperationModel import *


def dataChangeNotification(sender, e):
    # Display value.
    if e.Succeeded:
        print(e.Arguments.NodeDescriptor, ': ', e.AttributeData.Value, sep='')
    else:
        print(e.Arguments.NodeDescriptor, ' *** Failure: ', e.ErrorMessageBrief, sep='')


endpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:51210/UA/SampleServer')
# or 'http://opcua.demo-this.com:51211/UA/SampleServer' (currently not supported)
# or 'https://opcua.demo-this.com:51212/UA/SampleServer/'

# Instantiate the client object and hook events.
client = EasyUAClient()
client.DataChangeNotification += dataChangeNotification

# Obtain variables under "Scalar" node.
print('Browsing...')
try:
    nodeElementCollection = IEasyUAClientExtension.BrowseDataVariables(client,
        endpointDescriptor, UANodeDescriptor('nsu=http://test.org/UA/Data/ ;ns=2;i=10787'))
except UAException as uaException:
    print('*** Failure: ' + uaException.GetBaseException().Message)
    exit()

# Create array with monitored item arguments.
monitoredItemArgumentsArray = list(map(
    lambda element: EasyUAMonitoredItemArguments(None, endpointDescriptor, element.ToUANodeDescriptor()),
    nodeElementCollection))

print('Subscribing...')
client.SubscribeMultipleMonitoredItems(monitoredItemArgumentsArray)

print('Processing data change events for 20 seconds...')
time.sleep(20)

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

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

print('Finished.')

// Shows how to subscribe to complex data with OPC UA Complex Data plug-in.
//
// 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 OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples.ComplexData._EasyUAClient
{
    class SubscribeDataChange
    {
        public static void Main1()
        {
            // Define which server and node we will work with.
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";
            // or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            // or "https://opcua.demo-this.com:51212/UA/SampleServer/"
            UANodeDescriptor nodeDescriptor =
                "nsu=http://test.org/UA/Data/ ;i=10867"; // [ObjectsFolder]/Data.Dynamic.Scalar.StructureValue

            // Instantiate the client object and hook the event handler.
            var client = new EasyUAClient();
            client.DataChangeNotification += client_DataChangeNotification;

            // Subscribe to a node which returns complex data. This is done in the same way as regular subscribes - just 
            // the data returned is different.
            Console.WriteLine("Subscribing...");
            client.SubscribeDataChange(endpointDescriptor, nodeDescriptor, samplingInterval:1000);

            Console.WriteLine("Processing data change events for 20 seconds...");
            System.Threading.Thread.Sleep(20 * 1000);

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

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

            // Unhook the event handler.
            client.DataChangeNotification -= client_DataChangeNotification;


            // Example output:
            //
            //Subscribing...
            //Processing data change events for 20 seconds...
            //(ScalarValueDataType) structured
            //(ArrayValueDataType) structured
            //(ArrayValueDataType) structured
            //(ArrayValueDataType) structured
            //(ArrayValueDataType) structured
            //(ArrayValueDataType) structured
            //(ArrayValueDataType) structured
            //(ArrayValueDataType) structured
            //(ScalarValueDataType) structured
            //(ScalarValueDataType) structured
            //(ArrayValueDataType) structured
            //(ArrayValueDataType) structured
            //(ScalarValueDataType) structured
            //(ArrayValueDataType) structured
            //(ArrayValueDataType) structured
            //(ScalarValueDataType) structured
            //(ScalarValueDataType) structured
            //(ScalarValueDataType) structured
            //Unsubscribing...
            //Waiting for 5 seconds...
        }

        static void client_DataChangeNotification(object sender, EasyUADataChangeNotificationEventArgs e)
        {
            // Display value
            if (e.Succeeded)
                Console.WriteLine("Value: {0}", e.AttributeData.Value);
            else
                Console.WriteLine("*** Failure: {0}", e.ErrorMessageBrief);

            // For processing the internals of the data, refer to examples for GenericData and DataType classes.
        }
    }
}
' Shows how to subscribe to complex data with OPC UA Complex Data plug-in.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET .
' 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.

Imports System
Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace ComplexData._EasyUAClient

    Friend Class SubscribeDataChange

        Public Shared Sub Main1()

            ' Define which server we will work with.
            Dim endpointDescriptor As UAEndpointDescriptor =
                    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
            ' or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            ' or "https://opcua.demo-this.com:51212/UA/SampleServer/"

            ' Define which node we will work with.
            Dim nodeDescriptor As UANodeDescriptor = _
                "nsu=http://test.org/UA/Data/ ;i=10867"  ' [ObjectsFolder]/Data.Dynamic.Scalar.StructureValue

            ' Instantiate the client object and hook the event handler.
            Dim client = New EasyUAClient
            AddHandler client.DataChangeNotification, AddressOf client_DataChangeNotification

            ' Subscribe to a node which returns complex data. This is done in the same way as regular subscribes - just 
            ' the data returned is different.
            Console.WriteLine("Subscribing...")
            client.SubscribeDataChange(endpointDescriptor, nodeDescriptor, samplingInterval:=1000)

            Console.WriteLine("Processing data change events for 20 seconds...")
            Threading.Thread.Sleep((20 * 1000))

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

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

            ' Unhook the event handler.
            RemoveHandler client.DataChangeNotification, AddressOf client_DataChangeNotification


            ' Example output:
            '
            'Subscribing...
            'Processing data change events for 20 seconds...
            '(ScalarValueDataType) structured
            '(ArrayValueDataType) structured
            '(ArrayValueDataType) structured
            '(ArrayValueDataType) structured
            '(ArrayValueDataType) structured
            '(ArrayValueDataType) structured
            '(ArrayValueDataType) structured
            '(ArrayValueDataType) structured
            '(ScalarValueDataType) structured
            '(ScalarValueDataType) structured
            '(ArrayValueDataType) structured
            '(ArrayValueDataType) structured
            '(ScalarValueDataType) structured
            '(ArrayValueDataType) structured
            '(ArrayValueDataType) structured
            '(ScalarValueDataType) structured
            '(ScalarValueDataType) structured
            '(ScalarValueDataType) structured
            'Unsubscribing...
            'Waiting for 5 seconds...
        End Sub

        Private Shared Sub client_DataChangeNotification(sender As Object, e As EasyUADataChangeNotificationEventArgs)
            ' Display value
            If e.Succeeded Then
                Console.WriteLine("Value: {0}", e.AttributeData.Value)
            Else
                Console.WriteLine("*** Failure: {0}", e.ErrorMessageBrief)
            End If

            ' For processing the internals of the data, refer to examples for GenericData and DataType classes.
        End Sub
    End Class
End Namespace

// Shows how to subscribe to complex data with OPC UA Complex Data plug-in.
//
// 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
  TClientEventHandlers33 = class
    procedure OnDataChangeNotification(
      ASender: TObject;
      sender: OleVariant;
      const eventArgs: _EasyUADataChangeNotificationEventArgs);
  end;

procedure TClientEventHandlers33.OnDataChangeNotification(
  ASender: TObject;
  sender: OleVariant;
  const eventArgs: _EasyUADataChangeNotificationEventArgs);
begin
  // Display value
  if eventArgs.Succeeded then
      WriteLn('Value: ', eventArgs.AttributeData.Value.ToString)
  else
      WriteLn('*** Failure: ', eventArgs.ErrorMessageBrief);

  // For processing the internals of the data, refer to examples for GenericData and DataType classes.
end;

class procedure SubscribeDataChange.Main;
var
  Client: TEasyUAClient;
  ClientEventHandlers: TClientEventHandlers33;
  EndpointDescriptor: string;
  NodeDescriptor: string;
begin
  // Define which server and node we will work with.
  EndpointDescriptor := 
    //'http://opcua.demo-this.com:51211/UA/SampleServer';
    //'https://opcua.demo-this.com:51212/UA/SampleServer/';
    'opc.tcp://opcua.demo-this.com:51210/UA/SampleServer';
  NodeDescriptor := 'nsu=http://test.org/UA/Data/ ;i=10867';  // [ObjectsFolder]/Data.Dynamic.Scalar.StructureValue

  // Instantiate the client object and hook events
  Client := TEasyUAClient.Create(nil);
  ClientEventHandlers := TClientEventHandlers33.Create;
  Client.OnDataChangeNotification := ClientEventHandlers.OnDataChangeNotification;

  // Subscribe to a node which returns complex data. This is done in the same way as regular subscribes - just
  // the data returned is different.
  WriteLn('Subscribing...');
  Client.SubscribeDataChange(EndpointDescriptor, NodeDescriptor, 1000);

  WriteLn('Processing data change events for 20 seconds...');
  PumpSleep(20*1000);

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

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

  WriteLn('Finished.');
  FreeAndNil(Client);
  FreeAndNil(ClientEventHandlers);

  // Example output:
  //
  //Subscribing...
  //Processing data change events for 20 seconds...
  //(ScalarValueDataType) structured
  //(ArrayValueDataType) structured
  //(ArrayValueDataType) structured
  //(ArrayValueDataType) structured
  //(ArrayValueDataType) structured
  //(ArrayValueDataType) structured
  //(ArrayValueDataType) structured
  //(ArrayValueDataType) structured
  //(ScalarValueDataType) structured
  //(ScalarValueDataType) structured
  //(ArrayValueDataType) structured
  //(ArrayValueDataType) structured
  //(ScalarValueDataType) structured
  //(ArrayValueDataType) structured
  //(ArrayValueDataType) structured
  //(ScalarValueDataType) structured
  //(ScalarValueDataType) structured
  //(ScalarValueDataType) structured
  //Unsubscribing...
  //Waiting for 5 seconds...
end;
// Shows how to subscribe to complex data with OPC UA Complex Data plug-in.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in PHP on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-PHP .
// 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.

class ClientEvents {
    function DataChangeNotification($Sender, $E)
    {
        // Display value
        if ($E->Succeeded)
        printf("Value: %s\n", $E->AttributeData->Value);
        else
        printf("*** Failure : %s\n", $E->ErrorMessageBrief);
        // For processing the internals of the data, refer to examples for GenericData and DataType classes.
    }
}

// Define which server and node we will work with.
$EndpointDescriptor = 
    //"http://opcua.demo-this.com:51211/UA/SampleServer";
    //"https://opcua.demo-this.com:51212/UA/SampleServer/";
    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";
$NodeDescriptor = "nsu=http://test.org/UA/Data/ ;i=10867";  // [ObjectsFolder]/Data.Dynamic.Scalar.StructureValue

// Instantiate the client object and hook events
$Client = new COM("OpcLabs.EasyOpc.UA.EasyUAClient");
$ClientEvents = new ClientEvents();
com_event_sink($Client, $ClientEvents, "DEasyUAClientEvents");

// Subscribe to a node which returns complex data. This is done in the same way as regular subscribes - just
// the data returned is different.
printf("Subscribing...\n");
$Client->SubscribeDataChange($EndpointDescriptor, $NodeDescriptor, 1000);

printf("Processing data change events for 20 seconds...\n");
$startTime = time(); do { com_message_pump(1000); } while (time() < $startTime + 20);

printf("Unsubscribing...\n");
$Client->UnsubscribeAllMonitoredItems;

printf("Waiting for 5 seconds...\n");
$startTime = time(); do { com_message_pump(1000); } while (time() < $startTime + 5);

// This example shows how to store current state of the subscribed monitored items in a dictionary.
// each change.
//
// 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 System.Threading;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples._EasyUAClient
{
    partial class SubscribeMultipleMonitoredItems
    {
        public static void StoreInDictionary()
        {
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";
            // or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            // or "https://opcua.demo-this.com:51212/UA/SampleServer/"

            // Instantiate the client object and hook events.
            using (var client = new EasyUAClient())
            {
                client.DataChangeNotification += client_DataChangeNotification_StoreInDictionary;

                Console.WriteLine("Subscribing...");
                client.SubscribeMultipleMonitoredItems(new[]
                {
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor,
                        "nsu=http://test.org/UA/Data/ ;i=10845", 1000),
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor,
                        "nsu=http://test.org/UA/Data/ ;i=10853", 1000),
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor,
                        "nsu=http://test.org/UA/Data/ ;i=10855", 1000)
                });

                Console.WriteLine("Processing monitored item changed events for 1 minute...");
                int startTickCount = Environment.TickCount;
                do
                {
                    Thread.Sleep(5 * 1000);

                    // Each 5 seconds, display the current state of the monitored items we have subscribed to.
                    lock (_serialize)
                    {
                        Console.WriteLine();
                        foreach (KeyValuePair<UANodeDescriptor, UAAttributeDataResult> pair in _attributeDataResultDictionary)
                        {
                            UANodeDescriptor nodeDescriptor = pair.Key;
                            UAAttributeDataResult attributeDataResult = pair.Value;
                            Console.WriteLine($"{nodeDescriptor}: {attributeDataResult}");
                        }

                        // The code above shows how you can process the complete contents of the dictionary. In other
                        // scenarios, you may want to access just a specific entry in the dictionary. You can achieve that
                        // by indexing the dictionary by the node descriptor of the monitored item you are interested in.
                    }
                } while (Environment.TickCount < startTickCount + 60 * 1000);

                Console.WriteLine("Unsubscribing...");
            }

            Console.WriteLine("Finished.");
        }

        static void client_DataChangeNotification_StoreInDictionary(object sender, EasyUADataChangeNotificationEventArgs e)
        {
            lock (_serialize)
                // Convert the event arguments to a UAAttributeData result object, and store it in the dictionary under the
                // key which is the node descriptor of the monitored item this data change notification is for.
                _attributeDataResultDictionary[e.Arguments.NodeDescriptor] = (UAAttributeDataResult)e;
        }

        // Holds last known state of each subscribed monitored item.
        private static readonly Dictionary<UANodeDescriptor, UAAttributeDataResult> _attributeDataResultDictionary =
            new Dictionary<UANodeDescriptor, UAAttributeDataResult>();

        // Synchronization object used to prevent simultaneous access to the dictionary.
        private static readonly object _serialize = new object();
    }
}
' This example shows how to store current state of the subscribed monitored items in a dictionary.
' each change.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET .
' 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.

Imports System.Threading
Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace _EasyUAClient
    Partial Friend Class SubscribeMultipleMonitoredItems
        Public Shared Sub StoreInDictionary()

            ' Define which server we will work with.
            Dim endpointDescriptor As UAEndpointDescriptor =
                    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
            ' or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            ' or "https://opcua.demo-this.com:51212/UA/SampleServer/"

            ' Instantiate the client object.
            Using client = New EasyUAClient()
                AddHandler client.DataChangeNotification, AddressOf client_DataChangeNotification_StoreInDictionary

                Console.WriteLine("Subscribing...")
                client.SubscribeMultipleMonitoredItems(New EasyUAMonitoredItemArguments() {
                    New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor,
                        "nsu=http://test.org/UA/Data/ ;i=10845", 1000),
                    New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor,
                        "nsu=http://test.org/UA/Data/ ;i=10853", 1000),
                    New EasyUAMonitoredItemArguments(Nothing, endpointDescriptor,
                        "nsu=http://test.org/UA/Data/ ;i=10855", 1000)
                })

                Console.WriteLine("Processing monitored item changed events for 1 minute...")
                Dim startTickCount As Integer = Environment.TickCount
                Do
                    Thread.Sleep(5 * 1000)

                    ' Each 5 seconds, display the current state of the monitored items we have subscribed to.
                    SyncLock _serialize
                        Console.WriteLine()
                        For Each pair As KeyValuePair(Of UANodeDescriptor, UAAttributeDataResult) In _attributeDataResultDictionary
                            Dim nodeDescriptor As UANodeDescriptor = pair.Key
                            Dim attributeDataResult As UAAttributeDataResult = pair.Value
                            Console.WriteLine($"{nodeDescriptor}: {attributeDataResult}")
                        Next

                        ' The code above shows how you can process the complete contents of the dictionary. In other
                        ' scenarios, you may want to access just a specific entry in the dictionary. You can achieve that
                        ' by indexing the dictionary by the node descriptor of the monitored item you are interested in.
                    End SyncLock
                Loop While Environment.TickCount < startTickCount + 60 * 1000

                Console.WriteLine("Unsubscribing...")
            End Using

            Console.WriteLine("Finished.")
        End Sub

        Private Shared Sub client_DataChangeNotification_StoreInDictionary(ByVal sender As Object, ByVal e As EasyUADataChangeNotificationEventArgs)
            SyncLock _serialize
                ' Convert the event arguments to a UAAttributeData result object, and store it in the dictionary under the
                ' key which is the node descriptor of the monitored item this data change notification is for.
                _attributeDataResultDictionary(e.Arguments.NodeDescriptor) = CType(e, UAAttributeDataResult)
            End SyncLock

            ' Display value
            If e.Succeeded Then
                Console.WriteLine("{0}: {1}", e.Arguments.NodeDescriptor, e.AttributeData.Value)
            Else
                Console.WriteLine("{0} *** Failure: {1}", e.Arguments.NodeDescriptor, e.ErrorMessageBrief)
            End If
        End Sub

        ' Holds last known state of each subscribed monitores item.
        Private Shared ReadOnly _attributeDataResultDictionary As New Dictionary(Of UANodeDescriptor, UAAttributeDataResult)

        ' Synchronization object used to prevent simultaneous access to the dictionary.
        Private Shared ReadOnly _serialize As New Object
    End Class
End Namespace

# This example shows how to store current state of the subscribed monitored items in a dictionary.
# each change.
#
# 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 threading
import time

# Import .NET namespaces.
from OpcLabs.EasyOpc.UA import *
from OpcLabs.EasyOpc.UA.OperationModel import *


lock = threading.Lock()
attributeDataResultDictionary = {}

# Data change notification event handler.
def dataChangeNotification(sender, eventArgs):
    global lock
    global attributeDataResultDictionary
    with lock:
        # Convert the event arguments to a UAAttributeData result object, and store it in the dictionary under the
        # key which is the node descriptor of the monitored item this data change notification is for.
        attributeDataResultDictionary[eventArgs.Arguments.NodeDescriptor] = EasyUADataChangeNotificationEventArgs.ToUAAttributeDataResult(eventArgs)


endpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:51210/UA/SampleServer')
# or 'http://opcua.demo-this.com:51211/UA/SampleServer' (currently not supported)
# or 'https://opcua.demo-this.com:51212/UA/SampleServer/'

# Instantiate the client object.
client = EasyUAClient()
# Hook events.
client.DataChangeNotification += dataChangeNotification

print('Subscribing...')
client.SubscribeMultipleMonitoredItems([
    EasyUAMonitoredItemArguments(
        None,
        endpointDescriptor,
        UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10845'),
        UAMonitoringParameters(1000)),
    EasyUAMonitoredItemArguments(
        None,
        endpointDescriptor,
        UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10853'),
        UAMonitoringParameters(1000)),
    EasyUAMonitoredItemArguments(
        None,
        endpointDescriptor,
        UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10855'),
        UAMonitoringParameters(1000)),
    ])

print('Processing data change events for 1 minute...')
endTime = time.time() + 60
while time.time() < endTime:
    time.sleep(5)
    #
    # Each 5 seconds, display the current state of the monitored items we have subscribed to.
    with lock:
        print()
        print('Current state of the monitored items:')
        for nodeDescriptor, attributeDataResult in attributeDataResultDictionary.items():
            print(nodeDescriptor, ': ', attributeDataResult, sep='')
        #
        # The code above shows how you can process the complete contents of the dictionary. In other
        # scenarios, you may want to access just a specific entry in the dictionary. You can achieve that
        # by indexing the dictionary by the node descriptor of the monitored item you are interested in.

print()
print('Unsubscribing all monitored items...')
client.UnsubscribeAllMonitoredItems()

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

print('Finished.')
Requirements

Target Platforms: .NET Framework: Windows 10 (selected versions), Windows 11 (selected versions), Windows Server 2016, Windows Server 2022; .NET: Linux, macOS, Microsoft Windows

See Also

Reference

IEasyUAClient Interface
IEasyUAClient Members
SubscribeMultipleMonitoredItems Method

 

 

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