UnsubscribeMultipleItems Method (IEasyDAClient)

Unsubscribe from changes of multiple OPC items, specifying an enumerable of integer handles.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
Sub UnsubscribeMultipleItems( _
   ByVal handlesToUnsubscribe As IEnumerable(Of Integer) _
)

'Usage
 
Dim instance As IEasyDAClient
Dim handlesToUnsubscribe As IEnumerable(Of Integer)
 
instance.UnsubscribeMultipleItems(handlesToUnsubscribe)

void UnsubscribeMultipleItems( 
   IEnumerable<int> handlesToUnsubscribe
)

void UnsubscribeMultipleItems( 
   IEnumerable<int>^ handlesToUnsubscribe
)

Parameters

handlesToUnsubscribe: Subscription handles. Can be an array.

Exceptions

Exception Description

Exception	Description
System.ArgumentException	One of the arguments provided to a method is not valid. 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.

System.ArgumentException

One of the arguments provided to a method is not valid.

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 item subscription handles become invalid after this method is called.

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

.NET

// This example shows how to unsubscribe from changes of multiple items.

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

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

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

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

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

                Console.WriteLine("Unsubscribing from two items...");
                client.UnsubscribeMultipleItems(new [] {handleArray[1], handleArray[2]});

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

                Console.WriteLine("Unsubscribing from all remaining items...");
                client.UnsubscribeAllItems();

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


        // Example output:
        //
        //Subscribing...
        //handleArray(0): 12586002
        //handleArray(1) : 12586004
        //handleArray(2) : 12586005
        //handleArray(3) : 12586006
        //Processing item changed events for 10 seconds...
        //Simulation.Register_I4: 0 {System.Int32} @1601-01-01T00:00:00.000; GoodNonspecific(192)
        //Trends.Ramp(1 min): 0.585198730230331 {System.Double} @2020-04-10T15:50:35.111; GoodNonspecific(192)
        //Simulation.Random: 0.00125125888851588 {System.Double} @2020-04-10T15:50:35.111; GoodNonspecific(192)
        //Trends.Sine(1 min): -0.51011579179648 {System.Double} @2020-04-10T15:50:35.111; GoodNonspecific(192)
        //Trends.Ramp(1 min): 0.601875007152557 {System.Double} @2020-04-10T15:50:36.112; GoodNonspecific(192)
        //Simulation.Random: 0.56358531449324 {System.Double} @2020-04-10T15:50:36.112; GoodNonspecific(192)
        //Trends.Sine(1 min): -0.597275285519755 {System.Double} @2020-04-10T15:50:36.112; GoodNonspecific(192)
        //Trends.Ramp(1 min): 0.618548572063446 {System.Double} @2020-04-10T15:50:37.112; GoodNonspecific(192)
        //Simulation.Random: 0.193304239020966 {System.Double} @2020-04-10T15:50:37.112; GoodNonspecific(192)
        //Trends.Sine(1 min): -0.677870836926452 {System.Double} @2020-04-10T15:50:37.112; GoodNonspecific(192)
        //Trends.Ramp(1 min): 0.635226935148239 {System.Double} @2020-04-10T15:50:38.113; GoodNonspecific(192)
        //Simulation.Random: 0.808740501113926 {System.Double} @2020-04-10T15:50:38.113; GoodNonspecific(192)
        //Trends.Sine(1 min): -0.751053255223256 {System.Double} @2020-04-10T15:50:38.113; GoodNonspecific(192)
        //Trends.Ramp(1 min): 0.65190464258194 {System.Double} @2020-04-10T15:50:39.114; GoodNonspecific(192)
        //Simulation.Random: 0.58500930814539 {System.Double} @2020-04-10T15:50:39.114; GoodNonspecific(192)
        //Trends.Sine(1 min): -0.815993052494079 {System.Double} @2020-04-10T15:50:39.114; GoodNonspecific(192)
        //Trends.Ramp(1 min): 0.668579548597336 {System.Double} @2020-04-10T15:50:40.114; GoodNonspecific(192)
        //Simulation.Random: 0.47987304300058 {System.Double} @2020-04-10T15:50:40.114; GoodNonspecific(192)
        //Trends.Sine(1 min): -0.87197220432209 {System.Double} @2020-04-10T15:50:40.114; GoodNonspecific(192)
        //Trends.Ramp(1 min): 0.68526017665863 {System.Double} @2020-04-10T15:50:41.115; GoodNonspecific(192)
        //Simulation.Random: 0.350291451765496 {System.Double} @2020-04-10T15:50:41.115; GoodNonspecific(192)
        //Trends.Sine(1 min): -0.918402631917152 {System.Double} @2020-04-10T15:50:41.115; GoodNonspecific(192)
        //Trends.Ramp(1 min): 0.701931446790695 {System.Double} @2020-04-10T15:50:42.115; GoodNonspecific(192)
        //Simulation.Random: 0.895962401196326 {System.Double} @2020-04-10T15:50:42.115; GoodNonspecific(192)
        //Trends.Sine(1 min): -0.954736510704127 {System.Double} @2020-04-10T15:50:42.115; GoodNonspecific(192)
        //Trends.Ramp(1 min): 0.718607157468796 {System.Double} @2020-04-10T15:50:43.116; GoodNonspecific(192)
        //Simulation.Random: 0.822840052491836 {System.Double} @2020-04-10T15:50:43.116; GoodNonspecific(192)
        //Trends.Sine(1 min): -0.98060979065431 {System.Double} @2020-04-10T15:50:43.116; GoodNonspecific(192)
        //Trends.Ramp(1 min): 0.735284030437469 {System.Double} @2020-04-10T15:50:44.117; GoodNonspecific(192)
        //Simulation.Random: 0.746604815820795 {System.Double} @2020-04-10T15:50:44.117; GoodNonspecific(192)
        //Trends.Sine(1 min): -0.995728326344284 {System.Double} @2020-04-10T15:50:44.117; GoodNonspecific(192)
        //Unsubscribing from two items...
        //Processing item changed events for 10 seconds...
        //Simulation.Random: 0.174108096560564 { System.Double} @2020-04-10T15:50:45.117; GoodNonspecific(192)
        //Simulation.Random: 0.858943449201941 {System.Double} @2020-04-10T15:50:46.118; GoodNonspecific(192)
        //Simulation.Random: 0.710501419110691 {System.Double} @2020-04-10T15:50:47.118; GoodNonspecific(192)
        //Simulation.Random: 0.513534958952605 {System.Double} @2020-04-10T15:50:48.120; GoodNonspecific(192)
        //Simulation.Random: 0.303994872890408 {System.Double} @2020-04-10T15:50:49.120; GoodNonspecific(192)
        //Simulation.Random: 0.0149845881527146 {System.Double} @2020-04-10T15:50:50.121; GoodNonspecific(192)
        //Simulation.Random: 0.0914029358806116 {System.Double} @2020-04-10T15:50:51.122; GoodNonspecific(192)
        //Simulation.Random: 0.364452040162358 {System.Double} @2020-04-10T15:50:52.124; GoodNonspecific(192)
        //Simulation.Random: 0.147312845240638 {System.Double} @2020-04-10T15:50:53.125; GoodNonspecific(192)
        //Unsubscribing from all remaining items...
        //Waiting for 5 seconds...
    }
}

# This example shows how to unsubscribe from changes of multiple items.

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

# Import .NET namespaces.
from System.Collections.Generic import *
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 10 seconds...')
time.sleep(10)

print('Unsubscribing from two items...')
handleList = List[int]()
handleList.Add(handleArray[1])
handleList.Add(handleArray[2])
client.UnsubscribeMultipleItems(handleList)

print('Processing item change notifications for 10 seconds...')
time.sleep(10)

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

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

client.ItemChanged -= itemChanged

print('Finished.')

PHP
VBScript

// This example shows how to unsubscribe from changes of multiple items.

class DEasyDAClientEvents {
    function ItemChanged($varSender, $varE)
    {
        if ($varE->Succeeded)
        {
            printf(" s\n", $varE->Arguments->ItemDescriptor->ItemId, $varE->Vtq->ToString());
        }
        else
        {
            printf("*** Failure: %s\n", $varE->ErrorMessageBrief);
        }
    }
}

$ItemSubscriptionArguments1 = new COM("OpcLabs.EasyOpc.DataAccess.OperationModel.EasyDAItemSubscriptionArguments");
$ItemSubscriptionArguments1->ServerDescriptor->ServerClass = "OPCLabs.KitServer.2";
$ItemSubscriptionArguments1->ItemDescriptor->ItemID = "Simulation.Random";
$ItemSubscriptionArguments1->GroupParameters->RequestedUpdateRate = 1000;

$ItemSubscriptionArguments2 = new COM("OpcLabs.EasyOpc.DataAccess.OperationModel.EasyDAItemSubscriptionArguments");
$ItemSubscriptionArguments2->ServerDescriptor->ServerClass = "OPCLabs.KitServer.2";
$ItemSubscriptionArguments2->ItemDescriptor->ItemID = "Trends.Ramp (1 min)";
$ItemSubscriptionArguments2->GroupParameters->RequestedUpdateRate = 1000;

$ItemSubscriptionArguments3 = new COM("OpcLabs.EasyOpc.DataAccess.OperationModel.EasyDAItemSubscriptionArguments");
$ItemSubscriptionArguments3->ServerDescriptor->ServerClass = "OPCLabs.KitServer.2";
$ItemSubscriptionArguments3->ItemDescriptor->ItemID = "Trends.Sine (1 min)";
$ItemSubscriptionArguments3->GroupParameters->RequestedUpdateRate = 1000;

$ItemSubscriptionArguments4 = new COM("OpcLabs.EasyOpc.DataAccess.OperationModel.EasyDAItemSubscriptionArguments");
$ItemSubscriptionArguments4->ServerDescriptor->ServerClass = "OPCLabs.KitServer.2";
$ItemSubscriptionArguments4->ItemDescriptor->ItemID = "Simulation.Register_I4";
$ItemSubscriptionArguments4->GroupParameters->RequestedUpdateRate = 1000;

$arguments[0] = $ItemSubscriptionArguments1;
$arguments[1] = $ItemSubscriptionArguments2;
$arguments[2] = $ItemSubscriptionArguments3;
$arguments[3] = $ItemSubscriptionArguments4;

$Client = new COM("OpcLabs.EasyOpc.DataAccess.EasyDAClient");
$Events = new DEasyDAClientEvents();
com_event_sink($Client, $Events, "DEasyDAClientEvents");

print "Subscribing...\n";
$handleArray = $Client->SubscribeMultipleItems($arguments);

for ($i = 0; $i < count($handleArray); $i++)
{
    printf("handleArray[d]s\n", $i, $handleArray[$i]);
}

print "Processing item changed events for 10 seconds...\n";
$startTime = time(); do { com_message_pump(1000); } while (time() < $startTime + 10);

print "Unsubscribing from two items...\n";
$handles1[0] = $handleArray[1];
$handles1[1] = $handleArray[2];
$Client->UnsubscribeMultipleItems($handles1);

print "Processing item changed events for 10 seconds...\n";
$startTime = time(); do { com_message_pump(1000); } while (time() < $startTime + 10);

print "Unsubscribing from all remaining items...\n";
$Client->UnsubscribeAllItems;

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

Rem This example shows how to unsubscribe from changes of multiple items.

Option Explicit

Dim ItemSubscriptionArguments1: Set ItemSubscriptionArguments1 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.EasyDAItemSubscriptionArguments")
ItemSubscriptionArguments1.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ItemSubscriptionArguments1.ItemDescriptor.ItemID = "Simulation.Random"
ItemSubscriptionArguments1.GroupParameters.RequestedUpdateRate = 1000

Dim ItemSubscriptionArguments2: Set ItemSubscriptionArguments2 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.EasyDAItemSubscriptionArguments")
ItemSubscriptionArguments2.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ItemSubscriptionArguments2.ItemDescriptor.ItemID = "Trends.Ramp (1 min)"
ItemSubscriptionArguments2.GroupParameters.RequestedUpdateRate = 1000

Dim ItemSubscriptionArguments3: Set ItemSubscriptionArguments3 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.EasyDAItemSubscriptionArguments")
ItemSubscriptionArguments3.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ItemSubscriptionArguments3.ItemDescriptor.ItemID = "Trends.Sine (1 min)"
ItemSubscriptionArguments3.GroupParameters.RequestedUpdateRate = 1000

Dim ItemSubscriptionArguments4: Set ItemSubscriptionArguments4 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.EasyDAItemSubscriptionArguments")
ItemSubscriptionArguments4.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ItemSubscriptionArguments4.ItemDescriptor.ItemID = "Simulation.Register_I4"
ItemSubscriptionArguments4.GroupParameters.RequestedUpdateRate = 1000

Dim arguments(3)
Set arguments(0) = ItemSubscriptionArguments1
Set arguments(1) = ItemSubscriptionArguments2
Set arguments(2) = ItemSubscriptionArguments3
Set arguments(3) = ItemSubscriptionArguments4

Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient")
WScript.ConnectObject Client, "Client_"

WScript.Echo "Subscribing..."
Dim handleArray: handleArray = Client.SubscribeMultipleItems(arguments)

Dim i: For i = LBound(handleArray) To UBound(handleArray)
    WScript.Echo "handleArray(" & i & "): " & handleArray(i)
Next

WScript.Echo "Processing item changed events for 10 seconds..."
WScript.Sleep 10 * 1000

WScript.Echo "Unsubscribing from two items..."
Dim handles1(1)
handles1(0) = handleArray(1)
handles1(1) = handleArray(2)
Client.UnsubscribeMultipleItems handles1

WScript.Echo "Processing item changed events for 10 seconds..."
WScript.Sleep 10 * 1000

WScript.Echo "Unsubscribing from all remaining items..."
Client.UnsubscribeAllItems

WScript.Echo "Waiting for 5 seconds..."
WScript.Sleep 5 * 1000



Sub Client_ItemChanged(Sender, e)
    If Not (e.Succeeded) Then
        WScript.Echo "*** Failure: " & e.ErrorMessageBrief
        Exit Sub
    End If

    WScript.Echo e.Arguments.ItemDescriptor.ItemId & ": " & e.Vtq
End Sub

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

IEasyDAClient Interface
IEasyDAClient Members

Send Documentation Feedback. Resources: Knowledge Base. Technical support: Online Forums, FAQ.