ChangeItemSubscription(IEasyDAClient,Int32,DAGroupParameters) Method

Changes parameters of a subscription. Specify handle and group parameters.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<ExtensionAttribute()>
Public Overloads Shared Sub ChangeItemSubscription( _
   ByVal client As IEasyDAClient, _
   ByVal handle As Integer, _
   ByVal groupParameters As DAGroupParameters _
)

'Usage
 
Dim client As IEasyDAClient
Dim handle As Integer
Dim groupParameters As DAGroupParameters
 
IEasyDAClientExtension.ChangeItemSubscription(client, handle, groupParameters)

[Extension()]
public static void ChangeItemSubscription( 
   IEasyDAClient client,
   int handle,
   DAGroupParameters groupParameters
)

[Extension()]
public:
static void ChangeItemSubscription( 
   IEasyDAClient^ client,
   int handle,
   DAGroupParameters^ groupParameters
)

Parameters

client: The client object that will perform the operation.
handle: Item subscription handle as returned by the SubscribeItem method
groupParameters: An object containing new parameters of the subscription

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

It is more efficient to change multiple subscriptions using ChangeMultipleItemSubscriptions method.

Example

// This example shows how change the update rate of an existing subscription.

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

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

                Console.WriteLine("Subscribing...");
                int handle = client.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Random", 1000);

                Console.WriteLine("Waiting for 10 seconds...");
                Thread.Sleep(10 * 1000);

                Console.WriteLine("Changing subscription...");
                client.ChangeItemSubscription(handle, new DAGroupParameters(100));

                Console.WriteLine("Waiting for 10 seconds...");
                Thread.Sleep(10 * 1000);

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

                Console.WriteLine("Waiting for 10 seconds...");
                Thread.Sleep(10 * 1000);
            }
        }

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

# This example shows how change the update rate of an existing subscription.

# 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 *


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


# Instantiate the client object.
client = EasyDAClient()

client.ItemChanged += itemChanged

print('Subscribing item...')
handle = IEasyDAClientExtension.SubscribeItem(client, '', 'OPCLabs.KitServer.2', 'Simulation.Random', 1000)

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

print('Changing item subscription...')
IEasyDAClientExtension.ChangeItemSubscription(client, handle, DAGroupParameters(100))

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

print('Unsubscribing item...')
IEasyDAClientExtension.UnsubscribeItem(client, handle)

print('Waiting for 10 seconds...')
time.sleep(10)

client.ItemChanged -= itemChanged

print('Finished.')

' This example shows how change the update rate of an existing subscription.

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

Namespace DataAccess._EasyDAClient

    Partial Friend Class ChangeItemSubscription
        Public Shared Sub Main1()
            Using client = New EasyDAClient()
                AddHandler client.ItemChanged, AddressOf client_ItemChanged

                Console.WriteLine("Subscribing...")
                Dim handle As Integer = client.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Random", 1000)

                Console.WriteLine("Waiting for 10 seconds...")
                Thread.Sleep(10 * 1000)

                Console.WriteLine("Changing subscription...")
                client.ChangeItemSubscription(handle, New DAGroupParameters(100))

                Console.WriteLine("Waiting for 10 seconds...")
                Thread.Sleep(10 * 1000)

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

                Console.WriteLine("Waiting for 10 seconds...")
                Thread.Sleep(10 * 1000)
            End Using
        End Sub

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

CSharp
Python
VB.NET

// This example shows how change the update rate of an existing OPC XML-DA subscription.

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

namespace DocExamples.DataAccess.Xml
{
    class ChangeItemSubscription
    {
        public static void Main1Xml()
        {
            // Instantiate the client object.
            using (var client = new EasyDAClient())
            {
                client.ItemChanged += client_ItemChanged;

                Console.WriteLine("Subscribing...");
                int handle = client.SubscribeItem(
                    "http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx",
                    "Dynamic/Analog Types/Int",
                    2000,
                    state: null);

                Console.WriteLine("Waiting for 20 seconds...");
                Thread.Sleep(20 * 1000);

                Console.WriteLine("Changing subscription...");
                client.ChangeItemSubscription(handle, new DAGroupParameters(500));

                Console.WriteLine("Waiting for 10 seconds...");
                Thread.Sleep(10 * 1000);

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

                Console.WriteLine("Waiting for 10 seconds...");
                Thread.Sleep(10 * 1000);
            }
        }

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

# This example shows how change the update rate of an existing OPC XML-DA subscription.

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

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


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


# Instantiate the client object.
client = EasyDAClient()

client.ItemChanged += itemChanged

print('Subscribing item...')
handle = IEasyDAClientExtension.SubscribeItem(client,
    ServerDescriptor('http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx'),
    DAItemDescriptor('Dynamic/Analog Types/Int'),
    DAGroupParameters(2000),
    None) # state

print('Processing item change notifications for 20 seconds...')
time.sleep(20)

print('Changing item subscription...')
IEasyDAClientExtension.ChangeItemSubscription(client, handle, DAGroupParameters(500))

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

print('Unsubscribing item...')
IEasyDAClientExtension.UnsubscribeItem(client, handle)

print('Waiting for 10 seconds...')
time.sleep(10)

client.ItemChanged -= itemChanged

print('Finished.')

' This example shows how change the update rate of an existing OPC XML-DA subscription.

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

Namespace DataAccess.Xml

    Partial Friend Class ChangeItemSubscription
        Public Shared Sub Main1Xml()
            Using client = New EasyDAClient()
                AddHandler client.ItemChanged, AddressOf client_ItemChanged

                Console.WriteLine("Subscribing...")
                Dim handle As Integer = client.SubscribeItem(
                        "http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx",
                        "Dynamic/Analog Types/Int",
                        2000,
                        state:=Nothing)

                Console.WriteLine("Waiting for 20 seconds...")
                Thread.Sleep(20 * 1000)

                Console.WriteLine("Changing subscription...")
                client.ChangeItemSubscription(handle, New DAGroupParameters(500))

                Console.WriteLine("Waiting for 10 seconds...")
                Thread.Sleep(10 * 1000)

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

                Console.WriteLine("Waiting for 10 seconds...")
                Thread.Sleep(10 * 1000)
            End Using
        End Sub

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

CSharp
Python
VB.NET

// This example shows how change the update rate of an existing subscription.

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

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

                Console.WriteLine("Subscribing...");
                int handle = client.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Random", 1000);

                Console.WriteLine("Waiting for 10 seconds...");
                Thread.Sleep(10 * 1000);

                Console.WriteLine("Changing subscription...");
                client.ChangeItemSubscription(handle, new DAGroupParameters(100));

                Console.WriteLine("Waiting for 10 seconds...");
                Thread.Sleep(10 * 1000);

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

                Console.WriteLine("Waiting for 10 seconds...");
                Thread.Sleep(10 * 1000);
            }
        }

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

# This example shows how change the update rate of an existing subscription.

# 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 *


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


# Instantiate the client object.
client = EasyDAClient()

client.ItemChanged += itemChanged

print('Subscribing item...')
handle = IEasyDAClientExtension.SubscribeItem(client, '', 'OPCLabs.KitServer.2', 'Simulation.Random', 1000)

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

print('Changing item subscription...')
IEasyDAClientExtension.ChangeItemSubscription(client, handle, DAGroupParameters(100))

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

print('Unsubscribing item...')
IEasyDAClientExtension.UnsubscribeItem(client, handle)

print('Waiting for 10 seconds...')
time.sleep(10)

client.ItemChanged -= itemChanged

print('Finished.')

' This example shows how change the update rate of an existing subscription.

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

Namespace DataAccess._EasyDAClient

    Partial Friend Class ChangeItemSubscription
        Public Shared Sub Main1()
            Using client = New EasyDAClient()
                AddHandler client.ItemChanged, AddressOf client_ItemChanged

                Console.WriteLine("Subscribing...")
                Dim handle As Integer = client.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Random", 1000)

                Console.WriteLine("Waiting for 10 seconds...")
                Thread.Sleep(10 * 1000)

                Console.WriteLine("Changing subscription...")
                client.ChangeItemSubscription(handle, New DAGroupParameters(100))

                Console.WriteLine("Waiting for 10 seconds...")
                Thread.Sleep(10 * 1000)

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

                Console.WriteLine("Waiting for 10 seconds...")
                Thread.Sleep(10 * 1000)
            End Using
        End Sub

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

CSharp
Python
VB.NET

// This example shows how change the percent deadband of an existing subscription.

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

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

                Console.WriteLine("Subscribing with 10% deadband...");
                int handle = client.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Ramp 0:100 (10 s)",
                    VarTypes.Empty, requestedUpdateRate:100, percentDeadband:10.0f, state:null);

                Console.WriteLine("Waiting for 10 seconds...");
                Thread.Sleep(10 * 1000);

                Console.WriteLine("Changing subscription to 0% deadband...");
                client.ChangeItemSubscription(handle, new DAGroupParameters(100, 0.0f));

                Console.WriteLine("Waiting for 10 seconds...");
                Thread.Sleep(10 * 1000);

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

                Console.WriteLine("Waiting for 10 seconds...");
                Thread.Sleep(10 * 1000);
            }
        }

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

# This example shows how change the percent deadband of an existing subscription.

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

# Import .NET namespaces.
from OpcLabs.BaseLib.ComInterop import *
from OpcLabs.EasyOpc.DataAccess import *


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


# Instantiate the client object.
client = EasyDAClient()

client.ItemChanged += itemChanged

print('Subscribing item with 10% deadband...')
handle = IEasyDAClientExtension.SubscribeItem(client, '', 'OPCLabs.KitServer.2', 'Simulation.Ramp 0:100 (10 s)',
                                              VarType(VarTypes.Empty), requestedUpdateRate=50, percentDeadband=10.0,
                                              state=None)

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

print('Changing item subscription to 0% deadband...')
IEasyDAClientExtension.ChangeItemSubscription(client, handle, DAGroupParameters(50, 0.0))

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

print('Unsubscribing item...')
IEasyDAClientExtension.UnsubscribeItem(client, handle)

print('Waiting for 10 seconds...')
time.sleep(10)

client.ItemChanged -= itemChanged

print('Finished.')

' This example shows how change the percent deadband of an existing subscription.

Imports System.Threading
Imports OpcLabs.BaseLib.ComInterop
Imports OpcLabs.EasyOpc.DataAccess

Namespace DataAccess._EasyDAClient

    Partial Friend Class ChangeItemSubscription
        Public Shared Sub PercentDeadband()
            Using client = New EasyDAClient()
                AddHandler client.ItemChanged, AddressOf client_ItemChanged_PercentDeadband

                Console.WriteLine("Subscribing with 10% deadband...")
                Dim handle As Integer = client.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Ramp 0:100 (10 s)", VarTypes.Empty, 100, 10.0F, Nothing)

                Console.WriteLine("Waiting for 10 seconds...")
                Thread.Sleep(10 * 1000)

                Console.WriteLine("Changing subscription to 0% deadband...")
                client.ChangeItemSubscription(handle, New DAGroupParameters(100, 0.0F))

                Console.WriteLine("Waiting for 10 seconds...")
                Thread.Sleep(10 * 1000)

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

                Console.WriteLine("Waiting for 10 seconds...")
                Thread.Sleep(10 * 1000)
            End Using
        End Sub

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

CSharp
Python
VB.NET

// This example shows how change the update rate of an existing OPC XML-DA subscription.

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

namespace DocExamples.DataAccess.Xml
{
    class ChangeItemSubscription
    {
        public static void Main1Xml()
        {
            // Instantiate the client object.
            using (var client = new EasyDAClient())
            {
                client.ItemChanged += client_ItemChanged;

                Console.WriteLine("Subscribing...");
                int handle = client.SubscribeItem(
                    "http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx",
                    "Dynamic/Analog Types/Int",
                    2000,
                    state: null);

                Console.WriteLine("Waiting for 20 seconds...");
                Thread.Sleep(20 * 1000);

                Console.WriteLine("Changing subscription...");
                client.ChangeItemSubscription(handle, new DAGroupParameters(500));

                Console.WriteLine("Waiting for 10 seconds...");
                Thread.Sleep(10 * 1000);

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

                Console.WriteLine("Waiting for 10 seconds...");
                Thread.Sleep(10 * 1000);
            }
        }

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

# This example shows how change the update rate of an existing OPC XML-DA subscription.

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

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


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


# Instantiate the client object.
client = EasyDAClient()

client.ItemChanged += itemChanged

print('Subscribing item...')
handle = IEasyDAClientExtension.SubscribeItem(client,
    ServerDescriptor('http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx'),
    DAItemDescriptor('Dynamic/Analog Types/Int'),
    DAGroupParameters(2000),
    None) # state

print('Processing item change notifications for 20 seconds...')
time.sleep(20)

print('Changing item subscription...')
IEasyDAClientExtension.ChangeItemSubscription(client, handle, DAGroupParameters(500))

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

print('Unsubscribing item...')
IEasyDAClientExtension.UnsubscribeItem(client, handle)

print('Waiting for 10 seconds...')
time.sleep(10)

client.ItemChanged -= itemChanged

print('Finished.')

' This example shows how change the update rate of an existing OPC XML-DA subscription.

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

Namespace DataAccess.Xml

    Partial Friend Class ChangeItemSubscription
        Public Shared Sub Main1Xml()
            Using client = New EasyDAClient()
                AddHandler client.ItemChanged, AddressOf client_ItemChanged

                Console.WriteLine("Subscribing...")
                Dim handle As Integer = client.SubscribeItem(
                        "http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx",
                        "Dynamic/Analog Types/Int",
                        2000,
                        state:=Nothing)

                Console.WriteLine("Waiting for 20 seconds...")
                Thread.Sleep(20 * 1000)

                Console.WriteLine("Changing subscription...")
                client.ChangeItemSubscription(handle, New DAGroupParameters(500))

                Console.WriteLine("Waiting for 10 seconds...")
                Thread.Sleep(10 * 1000)

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

                Console.WriteLine("Waiting for 10 seconds...")
                Thread.Sleep(10 * 1000)
            End Using
        End Sub

        ' Item changed event handler
        Private Shared Sub client_ItemChanged(ByVal sender As Object, ByVal e As EasyDAItemChangedEventArgs)
            If e.Succeeded Then
                Console.WriteLine(e.Vtq)
            Else
                Console.WriteLine("*** Failure: {0}", 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

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