SubscribeMultipleItems(IEasyDAClient,DAItemGroupArguments[]) Method

Subscribe to changes of multiple OPC items. Subscribe to changes of multiple OPC items. The ItemChanged event will be generated for each significant item change. No callback methods will be invoked.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<ExtensionAttribute()>
<NotNullAttribute()>
Public Overloads Shared Function SubscribeMultipleItems( _
   ByVal client As IEasyDAClient, _
   ByVal itemGroupArgumentsArray() As DAItemGroupArguments _
) As Integer()

'Usage
 
Dim client As IEasyDAClient
Dim itemGroupArgumentsArray() As DAItemGroupArguments
Dim value() As Integer
 
value = IEasyDAClientExtension.SubscribeMultipleItems(client, itemGroupArgumentsArray)

[Extension()]
[NotNull()]
public static int[] SubscribeMultipleItems( 
   IEasyDAClient client,
   DAItemGroupArguments[] itemGroupArgumentsArray
)

[Extension()]
[NotNull()]
public:
static array<int>^ SubscribeMultipleItems( 
   IEasyDAClient^ client,
   array<DAItemGroupArguments^>^ itemGroupArgumentsArray
)

Parameters

client: The client object that will perform the operation.
itemGroupArgumentsArray: Array of arguments, one element per each OPC item involved in the operation.

Return Value

The function returns an array of integer handles. Each such uniquely identifies the item subscription. The indices of elements in the output array are the same as those in the input array, .

Exceptions

Exception Description

Exception	Description
System.ArgumentNullException	A `null` reference (`Nothing` in Visual Basic) is passed to a method that does not accept it as a valid argument. This is a usage error, i.e. it will never occur (the exception will not be thrown) in a correctly written program. Your code should not catch this exception.

System.ArgumentNullException

A null reference (Nothing in Visual Basic) is passed to a method that does not accept it as a valid argument.

This is a usage error, i.e. it will never occur (the exception will not be thrown) in a correctly written program. Your code should not catch this exception.

Remarks

The size of the input array will become the size of the output array. The element positions (indices) in the output array are the same as in the input array.

This method operates (at least in part) asynchronously, with respect to the caller. The actual execution of the operation may be delayed, and the outcome of the operation (if any) is provided to the calling code using an event notification, callback, or other means explained in the text. In a properly written program, this method does not throw any exceptions. You should therefore not put try/catch statements or similar constructs around calls to this method. The only exceptions thrown by this method are for usage errors, i.e. when your code violates the usage contract of the method, such as passing in invalid arguments or calling the method when the state of the object does not allow it. Any operation-related errors (i.e. errors that depend on external conditions that your code cannot reliably check) are indicated by the means the operation returns its outcome (if any), which is described in the text. For more information, see Do not catch any exceptions with asynchronous or multiple-operation methods.

Example

// Shows how different data types can be subscribed to, including rare types and arrays of values.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Threading;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.OperationModel;

namespace DocExamples.DataAccess._EasyDAClient
{
    partial class SubscribeMultipleItems
    {
        static void client_ItemChanged(object sender, EasyDAItemChangedEventArgs e)
        {
            Console.WriteLine();
            Console.WriteLine("Arguments.ItemDescriptor.ItemId: {0}", e.Arguments.ItemDescriptor.ItemId);

            if (e.Succeeded)
            {
                Debug.Assert(e.Vtq != null);
                Console.WriteLine("Vtq: {0}", e.Vtq);
            }
            else
                Console.WriteLine("*** Failure: {0}", e.ErrorMessageBrief);
        }

        public static void DataTypes()
        {
            IEnumerable<DAItemGroupArguments> arguments = new[]
                {
                    "Simulation.Register_EMPTY",
                    "Simulation.Register_NULL",
                    "Simulation.Register_DISPATCH",

                    "Simulation.ReadValue_I2",
                    "Simulation.ReadValue_I4",
                    "Simulation.ReadValue_R4",
                    "Simulation.ReadValue_R8",
                    "Simulation.ReadValue_CY",
                    "Simulation.ReadValue_DATE",
                    "Simulation.ReadValue_BSTR",
                    "Simulation.ReadValue_BOOL",
                    "Simulation.ReadValue_DECIMAL",
                    "Simulation.ReadValue_I1",
                    "Simulation.ReadValue_UI1",
                    "Simulation.ReadValue_UI2",
                    "Simulation.ReadValue_UI4",
                    "Simulation.ReadValue_INT",
                    "Simulation.ReadValue_UINT",

                    "Simulation.ReadValue_ArrayOfI2",
                    "Simulation.ReadValue_ArrayOfI4",
                    "Simulation.ReadValue_ArrayOfR4",
                    "Simulation.ReadValue_ArrayOfR8",
                    "Simulation.ReadValue_ArrayOfCY",
                    "Simulation.ReadValue_ArrayOfDATE",
                    "Simulation.ReadValue_ArrayOfBSTR",
                    "Simulation.ReadValue_ArrayOfBOOL",
                    //"Simulation.ReadValue_ArrayOfDECIMAL",
                    "Simulation.ReadValue_ArrayOfI1",
                    "Simulation.ReadValue_ArrayOfUI1",
                    "Simulation.ReadValue_ArrayOfUI2",
                    "Simulation.ReadValue_ArrayOfUI4",
                    "Simulation.ReadValue_ArrayOfINT",
                    "Simulation.ReadValue_ArrayOfUINT",
                }.Select(itemId => new DAItemGroupArguments("", "OPCLabs.KitServer.2", itemId, 3 * 1000, null));

            // Instantiate the client object.
            var client = new EasyDAClient();
            client.ItemChanged += client_ItemChanged;

            Console.WriteLine("Subscribing items...");
            client.SubscribeMultipleItems(arguments.ToArray());
            Thread.Sleep(30 * 1000);
            client.UnsubscribeAllItems();
            client.ItemChanged -= client_ItemChanged;
        }
    }
}

# Shows how different data types can be subscribed to, including rare types and arrays of values.

# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc
import time

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


# Item changed event handler.
def itemChanged(sender, e):
    print()
    print('Arguments.ItemDescriptor.ItemId: ', e.Arguments.ItemDescriptor.ItemId, sep='')

    if e.Succeeded:
        assert e.Vtq is not None
        print('Vtq: ', e.Vtq, sep='')
    else:
        print(' *** Failure: ', e.ErrorMessageBrief, sep='')


#
itemIds = [
    'Simulation.Register_EMPTY',
    'Simulation.Register_NULL',
    'Simulation.Register_DISPATCH',

    'Simulation.ReadValue_I2',
    'Simulation.ReadValue_I4',
    'Simulation.ReadValue_R4',
    'Simulation.ReadValue_R8',
    'Simulation.ReadValue_CY',
    'Simulation.ReadValue_DATE',
    'Simulation.ReadValue_BSTR',
    'Simulation.ReadValue_BOOL',
    'Simulation.ReadValue_DECIMAL',
    'Simulation.ReadValue_I1',
    'Simulation.ReadValue_UI1',
    'Simulation.ReadValue_UI2',
    'Simulation.ReadValue_UI4',
    'Simulation.ReadValue_INT',
    'Simulation.ReadValue_UINT',

    'Simulation.ReadValue_ArrayOfI2',
    'Simulation.ReadValue_ArrayOfI4',
    'Simulation.ReadValue_ArrayOfR4',
    'Simulation.ReadValue_ArrayOfR8',
    'Simulation.ReadValue_ArrayOfCY',
    'Simulation.ReadValue_ArrayOfDATE',
    'Simulation.ReadValue_ArrayOfBSTR',
    'Simulation.ReadValue_ArrayOfBOOL',
    # 'Simulation.ReadValue_ArrayOfDECIMAL',
    'Simulation.ReadValue_ArrayOfI1',
    'Simulation.ReadValue_ArrayOfUI1',
    'Simulation.ReadValue_ArrayOfUI2',
    'Simulation.ReadValue_ArrayOfUI4',
    'Simulation.ReadValue_ArrayOfINT',
    'Simulation.ReadValue_ArrayOfUINT',
]
arguments = map(lambda itemId: DAItemGroupArguments('', 'OPCLabs.KitServer.2', itemId, 3*1000, None), itemIds)

# Instantiate the client object.
client = EasyDAClient()
client.ItemChanged += itemChanged

print('Subscribing item changes...')
IEasyDAClientExtension.SubscribeMultipleItems(client, arguments)

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

print('Unsubscribing all items...')
client.UnsubscribeAllItems()

client.ItemChanged -= itemChanged
print('Finished.')

' Shows how different data types can be subscribed to, including rare types and arrays of values.

Imports System.Threading
Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.DataAccess.OperationModel

Namespace DataAccess._EasyDAClient
    Partial Friend Class SubscribeMultipleItems
        Private Shared Sub client_ItemChanged(sender As Object, e As EasyDAItemChangedEventArgs)

            Console.WriteLine()
            Console.WriteLine("ItemDescriptor.Arguments.ItemId: {0}", e.Arguments.ItemDescriptor.ItemId)
            If e.Succeeded Then
                Debug.Assert(e.Vtq IsNot Nothing)
                Console.WriteLine("Vtq: {0}", e.Vtq)
            Else
                Console.WriteLine("*** Failure: {0}", e.ErrorMessageBrief)
            End If
        End Sub

        Shared Sub DataTypes()
            Dim arguments As IEnumerable(Of DAItemGroupArguments) = New String() _
            { _
                "Simulation.Register_EMPTY",
                "Simulation.Register_NULL",
                "Simulation.Register_DISPATCH",
 _
                "Simulation.ReadValue_I2",
                "Simulation.ReadValue_I4",
                "Simulation.ReadValue_R4",
                "Simulation.ReadValue_R8",
                "Simulation.ReadValue_CY",
                "Simulation.ReadValue_DATE",
                "Simulation.ReadValue_BSTR",
                "Simulation.ReadValue_BOOL",
                "Simulation.ReadValue_DECIMAL",
                "Simulation.ReadValue_I1",
                "Simulation.ReadValue_UI1",
                "Simulation.ReadValue_UI2",
                "Simulation.ReadValue_UI4",
                "Simulation.ReadValue_INT",
                "Simulation.ReadValue_UINT",
 _
                "Simulation.ReadValue_ArrayOfI2",
                "Simulation.ReadValue_ArrayOfI4",
                "Simulation.ReadValue_ArrayOfR4",
                "Simulation.ReadValue_ArrayOfR8",
                "Simulation.ReadValue_ArrayOfCY",
                "Simulation.ReadValue_ArrayOfDATE",
                "Simulation.ReadValue_ArrayOfBSTR",
                "Simulation.ReadValue_ArrayOfBOOL",
                "Simulation.ReadValue_ArrayOfI1",
                "Simulation.ReadValue_ArrayOfUI1",
                "Simulation.ReadValue_ArrayOfUI2",
                "Simulation.ReadValue_ArrayOfUI4",
                "Simulation.ReadValue_ArrayOfINT",
                "Simulation.ReadValue_ArrayOfUINT"
            } _
            .Select(Function(itemId) New DAItemGroupArguments("", "OPCLabs.KitServer.2", itemId, 3 * 1000, Nothing))

            Console.WriteLine()

            Dim client As New EasyDAClient()
            Dim eventHandler = New EasyDAItemChangedEventHandler(AddressOf client_ItemChanged)
            AddHandler client.ItemChanged, eventHandler

            Console.WriteLine("Subscribing items...")
            client.SubscribeMultipleItems(arguments.ToArray())
            Thread.Sleep(30 * 1000)
            client.UnsubscribeAllItems()
            RemoveHandler client.ItemChanged, eventHandler
        End Sub
    End Class
End Namespace

CSharp
PowerShell
Python
VB.NET

// This example shows how subscribe to changes of multiple items and display the value of the item with each change.

using System;
using System.Threading;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.OperationModel;

namespace DocExamples.DataAccess._EasyDAClient
{
    partial class SubscribeMultipleItems
    {
        public static void Main1()
        {
            // Instantiate the client object.
            using (var client = new EasyDAClient())
            {
                client.ItemChanged += client_Main1_ItemChanged;

                Console.WriteLine("Subscribing item changes...");
                client.SubscribeMultipleItems(
                    new[] {
                            new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, null), 
                            new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Ramp (1 min)", 1000, null), 
                            new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Sine (1 min)", 1000, null),  
                            new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Register_I4", 1000, null)
                        });

                Console.WriteLine("Processing item changed events for 1 minute...");
                Thread.Sleep(60 * 1000);

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

            Console.WriteLine("Finished.");
        }

        // Item changed event handler
        static void client_Main1_ItemChanged(object sender, EasyDAItemChangedEventArgs e)
        {
            if (e.Succeeded)
                Console.WriteLine($"{e.Arguments.ItemDescriptor.ItemId}: {e.Vtq}");
            else
                Console.WriteLine($"{e.Arguments.ItemDescriptor.ItemId} *** Failure: {e.ErrorMessageBrief}");
        }
    }
}

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

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

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

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

# Item changed event handler
Register-ObjectEvent -InputObject $client -EventName ItemChanged -Action { 
    if ($EventArgs.Succeeded) {
        Write-Host "$($EventArgs.Arguments.ItemDescriptor.ItemId): $($EventArgs.Vtq)"
    }
    else {
        Write-Host "$($EventArgs.Arguments.ItemDescriptor.ItemId) *** Failure: $($EventArgs.ErrorMessageBrief)"
    }
}

Write-Host "Subscribing item changes..."
$handleArray = [IEasyDAClientExtension]::SubscribeMultipleItems($client, @(
    (New-Object DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, $null)),
    (New-Object DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Ramp (1 min)", 1000, $null)),
    (New-Object DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Sine (1 min)", 1000, $null)),
    (New-Object DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Register_I4", 1000, $null))
    ))

Write-Host "Processing item changed events for 1 minute..."
$stopwatch =  [System.Diagnostics.Stopwatch]::StartNew() 
while ($stopwatch.Elapsed.TotalSeconds -lt 30) {    
    Start-Sleep -Seconds 1
}

Write-Host "Unsubscribing item changes..."
$client.UnsubscribeAllItems()

Write-Host "Finished."

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

# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc
import time

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


# Item changed event handler.
def itemChanged(sender, e):
    if e.Succeeded:
        print(e.Arguments.ItemDescriptor.ItemId, ': ', e.Vtq, sep='')
    else:
        print(e.Arguments.ItemDescriptor.ItemId, ' *** Failure: ', e.ErrorMessageBrief, sep='')


# Instantiate the client object.
client = EasyDAClient()

client.ItemChanged += itemChanged

print('Subscribing item changes...')
client.SubscribeMultipleItems([
    EasyDAItemSubscriptionArguments('', 'OPCLabs.KitServer.2', 'Simulation.Random', 1000, None),
    EasyDAItemSubscriptionArguments('', 'OPCLabs.KitServer.2', 'Trends.Ramp (1 min)', 1000, None),
    EasyDAItemSubscriptionArguments('', 'OPCLabs.KitServer.2', 'Trends.Sine (1 min)', 1000, None),
    EasyDAItemSubscriptionArguments('', 'OPCLabs.KitServer.2', 'Simulation.Register_I4', 1000, None),
    ])

print('Processing item change notifications for 1 minute...')
time.sleep(60)

print('Unsubscribing all items...')
client.UnsubscribeAllItems()

client.ItemChanged -= itemChanged

print('Finished.')

' This example shows how subscribe to changes of multiple items and display the value of the item with each change.

Imports System.Threading
Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.DataAccess.OperationModel

Namespace DataAccess._EasyDAClient
    Partial Friend Class SubscribeMultipleItems
        Public Shared Sub Main1()
            Using client = New EasyDAClient()
                AddHandler client.ItemChanged, AddressOf client_ItemChanged_Main1

                client.SubscribeMultipleItems(New DAItemGroupArguments() { _
                 New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, Nothing), _
                 New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Ramp (1 min)", 1000, Nothing), _
                 New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Sine (1 min)", 1000, Nothing), _
                 New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Register_I4", 1000, Nothing) _
                })

                Console.WriteLine("Processing item changed events for 1 minute...")
                Thread.Sleep(60 * 1000)
            End Using
        End Sub

        ' Item changed event handler
        Private Shared Sub client_ItemChanged_Main1(ByVal sender As Object, ByVal e As EasyDAItemChangedEventArgs)
            ' Display the data
            If e.Succeeded Then
                Console.WriteLine("{0}: {1}", e.Arguments.ItemDescriptor.ItemId, e.Vtq)
            Else
                Console.WriteLine("{0} *** Failure: {1}", e.Arguments.ItemDescriptor.ItemId, e.ErrorMessageBrief)
            End If
        End Sub
    End Class
End Namespace

CSharp
Python
VB.NET

// This example shows how subscribe to large number of items.

using System;
using System.Threading;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.OperationModel;

namespace DocExamples.DataAccess._EasyDAClient
{
    partial class SubscribeMultipleItems
    {
        public static void ManyItems()
        {
            // Instantiate the client object.
            using (var client = new EasyDAClient())
            {
                client.ItemChanged += client_ItemChanged_ManyItems;

                const int numberOfItems = 1000;

                Console.WriteLine("Preparing arguments...");
                var argumentArray = new DAItemGroupArguments[numberOfItems];
                for (int i = 0; i < numberOfItems; i++)
                {
                    int copy = (i / 100) + 1;
                    int phase = (i % 100) + 1;
                    string itemId = String.Format("Simulation.Incrementing.Copy_{0}.Phase_{1}", copy, phase);
                    argumentArray[i] = new DAItemGroupArguments("", "OPCLabs.KitServer.2", itemId, 50, null);
                }

                Console.WriteLine("Subscribing to {0} items...", numberOfItems);
                client.SubscribeMultipleItems(argumentArray);

                Console.WriteLine("Processing item changed events for 1 minute...");
                Thread.Sleep(60 * 1000);
            }
        }

        // Item changed event handler
        static void client_ItemChanged_ManyItems(object sender, EasyDAItemChangedEventArgs e)
        {
            if (e.Succeeded)
                Console.WriteLine("{0}: {1}", e.Arguments.ItemDescriptor.ItemId, e.Vtq);
            else
                Console.WriteLine("{0} *** Failure: {1}", e.Arguments.ItemDescriptor.ItemId, e.ErrorMessageBrief);
        }
    }
}

# This example shows how subscribe to large number of items.

# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc
import time

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


# Item changed event handler.
def itemChanged(sender, e):
    if e.Succeeded:
        print(e.Arguments.ItemDescriptor.ItemId, ': ', e.Vtq, sep='')
    else:
        print(e.Arguments.ItemDescriptor.ItemId, ' *** Failure: ', e.ErrorMessageBrief, sep='')


NUMBER_OF_ITEMS = 1000

# Instantiate the client object.
client = EasyDAClient()

client.ItemChanged += itemChanged

print('Creating array of arguments...')
argumentArray = [None]*NUMBER_OF_ITEMS
for i in range(NUMBER_OF_ITEMS):
    copy = (i//100) + 1
    phase = i % 100
    itemId = 'Simulation.Incrementing.Copy_{}.Phase_{}'.format(copy, phase)
    print(itemId)
    #
    itemGroupArguments = DAItemGroupArguments('', 'OPCLabs.KitServer.2', itemId, 50, None)
    argumentArray[i] = itemGroupArguments

print('Subscribing to changes of ', NUMBER_OF_ITEMS, ' items...')
IEasyDAClientExtension.SubscribeMultipleItems(client, argumentArray)

print('Processing item change notifications for 1 minute...')
time.sleep(60)

print('Unsubscribing all items...')
client.UnsubscribeAllItems()

client.ItemChanged -= itemChanged

print('Finished.')

' This example shows how subscribe to large number of items.

Imports System.Threading
Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.DataAccess.OperationModel

Namespace DataAccess._EasyDAClient
    Partial Friend Class SubscribeMultipleItems
        Public Shared Sub ManyItems()
            Using client = New EasyDAClient()
                AddHandler client.ItemChanged, AddressOf client_ItemChanged_ManyItems

                Const numberOfItems As Integer = 1000

                Console.WriteLine("Preparing arguments...")
                Dim argumentArray = New DAItemGroupArguments(numberOfItems - 1) {}
                For i As Integer = 0 To numberOfItems - 1
                    Dim copy As Integer = (i \ 100) + 1
                    Dim phase As Integer = (i Mod 100) + 1
                    Dim itemId As String = String.Format("Simulation.Incrementing.Copy_{0}.Phase_{1}", copy, phase)
                    argumentArray(i) = New DAItemGroupArguments("", "OPCLabs.KitServer.2", itemId, 50, Nothing)
                Next i

                Console.WriteLine("Subscribing to {0} items...", numberOfItems)
                client.SubscribeMultipleItems(argumentArray)

                Console.WriteLine("Processing item changed events for 1 minute...")
                Thread.Sleep(60 * 1000)
            End Using
        End Sub

        ' Item changed event handler
        Private Shared Sub client_ItemChanged_ManyItems(ByVal sender As Object, ByVal e As EasyDAItemChangedEventArgs)
            ' Display the data
            If e.Succeeded Then
                Console.WriteLine("{0}: {1}", e.Arguments.ItemDescriptor.ItemId, e.Vtq)
            Else
                Console.WriteLine("{0} *** Failure: {1}", e.Arguments.ItemDescriptor.ItemId, e.ErrorMessageBrief)
            End If
        End Sub
    End Class
End Namespace

CSharp
Python
VB.NET

// This example shows how subscribe to changes of multiple items, and unsubscribe from one of them.

using System;
using System.Threading;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.OperationModel;

namespace DocExamples.DataAccess._EasyDAClient
{
    class UnsubscribeItem
    {
        public static void Main1()
        {
            // Instantiate the client object.
            using (var client = new EasyDAClient())
            {
                client.ItemChanged += client_ItemChanged;

                int[] handleArray = client.SubscribeMultipleItems(
                    new[] {
                            new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, null), 
                            new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Ramp (1 min)", 1000, null), 
                            new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Sine (1 min)", 1000, null),  
                            new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Register_I4", 1000, null)
                        });

                Console.WriteLine("Processing item changed events for 30 seconds...");
                Thread.Sleep(30 * 1000);

                Console.WriteLine("Unsubscribing from the first item...");
                client.UnsubscribeItem(handleArray[0]);

                Console.WriteLine();

                Console.WriteLine("Processing item changed events for 30 seconds...");
                Thread.Sleep(30 * 1000);
            }
        }

        // Item changed event handler
        static void client_ItemChanged(object sender, EasyDAItemChangedEventArgs e)
        {
            if (e.Succeeded)
                Console.WriteLine("{0}: {1}", e.Arguments.ItemDescriptor.ItemId, e.Vtq);
            else
                Console.WriteLine("{0} *** Failure: {1}", e.Arguments.ItemDescriptor.ItemId, e.ErrorMessageBrief);
        }
    }
}

# This example shows how subscribe to changes of multiple items, and unsubscribe from one of them.

# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc
import time

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


# Item changed event handler.
def itemChanged(sender, e):
    if e.Succeeded:
        print(e.Arguments.ItemDescriptor.ItemId, ': ', e.Vtq, sep='')
    else:
        print(e.Arguments.ItemDescriptor.ItemId, ' *** Failure: ', e.ErrorMessageBrief, sep='')


# Instantiate the client object.
client = EasyDAClient()

client.ItemChanged += itemChanged

print('Subscribing item changes...')
handleArray = client.SubscribeMultipleItems([
    EasyDAItemSubscriptionArguments('', 'OPCLabs.KitServer.2', 'Simulation.Random', 1000, None),
    EasyDAItemSubscriptionArguments('', 'OPCLabs.KitServer.2', 'Trends.Ramp (1 min)', 1000, None),
    EasyDAItemSubscriptionArguments('', 'OPCLabs.KitServer.2', 'Trends.Sine (1 min)', 1000, None),
    EasyDAItemSubscriptionArguments('', 'OPCLabs.KitServer.2', 'Simulation.Register_I4', 1000, None),
    ])

for i in range(len(handleArray)):
    print('handleArray[', i, ']: ', handleArray[i], sep='')

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

print('Unsubscribing from the first item...')
IEasyDAClientExtension.UnsubscribeItem(client, handleArray[0])

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

client.ItemChanged -= itemChanged

print('Finished.')

' This example shows how subscribe to changes of multiple items, and unsubscribe from one of them.

Imports System.Threading
Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.DataAccess.OperationModel

Namespace DataAccess._EasyDAClient
    Partial Friend Class UnsubscribeItem
        Shared Sub Main1()
            Using client = New EasyDAClient()
                AddHandler client.ItemChanged, AddressOf client_ItemChanged

                Dim handleArray = client.SubscribeMultipleItems(
                        New DAItemGroupArguments() _
                        { _
                            New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, Nothing),
                            New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Ramp (1 min)", 1000, Nothing),
                            New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Sine (1 min)", 1000, Nothing),
                            New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Register_I4", 1000, Nothing)
                        })

                Console.WriteLine("Processing item changed events for 30 seconds...")
                Thread.Sleep(30 * 1000)

                Console.WriteLine("Unsubscribing from the first item...")
                client.UnsubscribeItem(handleArray(0))

                Console.WriteLine()

                Console.WriteLine("Processing item changed events for 30 seconds...")
                Thread.Sleep(30 * 1000)
            End Using
        End Sub

        ' Item changed event handler
        Private Shared Sub client_ItemChanged(sender As Object, e As EasyDAItemChangedEventArgs)
            If e.Succeeded Then
                Console.WriteLine("{0}: {1}", e.Arguments.ItemDescriptor.ItemId, e.Vtq)
            Else
                Console.WriteLine("{0} *** Failure: {1}", e.Arguments.ItemDescriptor.ItemId, e.ErrorMessageBrief)
            End If
        End Sub
    End Class
End Namespace

Requirements

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

Reference

IEasyDAClientExtension Class
IEasyDAClientExtension Members
Overload List

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