OPC Studio User's Guide and Reference
PullItemChanged Method (IEasyDAClientExtension)
Example 



OpcLabs.EasyOpcClassicCore Assembly > OpcLabs.EasyOpc.DataAccess Namespace > IEasyDAClientExtension Class : PullItemChanged Method
The client object that will perform the operation.
The number of milliseconds to wait, or System.Threading.Timeout.Infinite (-1) to wait indefinitely.
Attempts to pull an OPC item change subscribed to by the SubscribeMultipleItems or SubscribeItem method.
Syntax
'Declaration
 

<ExtensionAttribute()>
<CanBeNullAttribute()>
Public Shared Function PullItemChanged( _
   ByVal client As IEasyDAClient, _
   ByVal millisecondsTimeout As Integer _
) As EasyDAItemChangedEventArgs
'Usage
 

Dim client As IEasyDAClient
Dim millisecondsTimeout As Integer
Dim value As EasyDAItemChangedEventArgs
 
value = IEasyDAClientExtension.PullItemChanged(client, millisecondsTimeout)
[Extension()]
[CanBeNull()]
public static EasyDAItemChangedEventArgs PullItemChanged( 
   IEasyDAClient client,
   int millisecondsTimeout
)
[Extension()]
[CanBeNull()]
public:
static EasyDAItemChangedEventArgs^ PullItemChanged( 
   IEasyDAClient^ client,
   int millisecondsTimeout
)

Parameters

client
The client object that will perform the operation.
millisecondsTimeout
The number of milliseconds to wait, or System.Threading.Timeout.Infinite (-1) to wait indefinitely.

Return Value

The event arguments, or null if no event is available within the specified time.
Exceptions
ExceptionDescription
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.ArgumentOutOfRangeException

The value of an argument is outside the allowable range of values as defined by the invoked method.

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.

Example

.NET

.NET

.NET

// This example shows how to subscribe to item changes and obtain the events by pulling them.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

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

namespace DocExamples.DataAccess._EasyDAClient
{
    partial class PullItemChanged
    {
        public static void Main1()
        {
            // Instantiate the client object.
            // In order to use event pull, you must set a non-zero queue capacity upfront.
            var client = new EasyDAClient { PullItemChangedQueueCapacity = 1000 };

            Console.WriteLine("Subscribing item changes...");
            client.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Random", 1000);

            Console.WriteLine("Processing item changes for 1 minute...");
            int endTick = Environment.TickCount + 60 * 1000;
            do
            {
                EasyDAItemChangedEventArgs eventArgs = client.PullItemChanged(2 * 1000);
                if (!(eventArgs is null))
                    // Handle the notification event
                    Console.WriteLine(eventArgs);
            } while (Environment.TickCount < endTick);

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

            Console.WriteLine("Finished.");
        }
    }
}
# This example shows how to subscribe to item changes and obtain the events by pulling them.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

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

# 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
# In order to use event pull, you must set a non-zero queue capacity upfront.
$client.PullItemChangedQueueCapacity = 1000

Write-Host "Subscribing item..."
[IEasyDAClientExtension]::SubscribeItem($client, "", "OPCLabs.KitServer.2", "Simulation.Random", 1000)

Write-Host "Processing item changes for 1 minute..."
$stopwatch =  [System.Diagnostics.Stopwatch]::StartNew() 
while ($stopwatch.Elapsed.TotalSeconds -lt 60) {    
    $eventArgs = [IEasyDAClientExtension]::PullItemChanged($client, 2*1000)
    if ($eventArgs -ne $null) {
        # Handle the notification event
        Write-Host $eventArgs
    }
}

Write-Host "Unsubscribing items..."
$client.UnsubscribeAllItems()

Write-Host "Finished."

# This example shows how to subscribe to item changes and obtain the events by pulling them.
#
# 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 .
# 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 *


# Instantiate the client object
client = EasyDAClient()
# In order to use event pull, you must set a non-zero queue capacity upfront.
client.PullItemChangedQueueCapacity = 1000

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

print('Processing item changes for 1 minute...')
endTime = time.time() + 60
while time.time() < endTime:
    eventArgs = IEasyDAClientExtension.PullItemChanged(client, 2*1000)
    if eventArgs is not None:
        # Handle the notification event
        print(eventArgs)

print('Unsubscribing item changes...')
client.UnsubscribeAllItems()

print('Finished.')

' This example shows how to subscribe to item changes and obtain the events by pulling them.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.DataAccess.OperationModel

Namespace DataAccess._EasyDAClient
    Partial Friend Class PullItemChanged
        Public Shared Sub Main1()
            Dim client = New EasyDAClient()
            ' In order to use event pull, you must set a non-zero queue capacity upfront.
            client.PullItemChangedQueueCapacity = 1000

            Console.WriteLine("Subscribing item changes...")
            client.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Random", 1000)

            Console.WriteLine("Processing item changes for 1 minute...")
            Dim endTick As Integer = Environment.TickCount + 60 * 1000
            Do
                Dim eventArgs As EasyDAItemChangedEventArgs = client.PullItemChanged(2 * 1000)
                If Not eventArgs Is Nothing Then
                    ' Handle the notification event
                    Console.WriteLine(eventArgs)
                End If
            Loop While Environment.TickCount < endTick

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

            Console.WriteLine("Finished.")
        End Sub
    End Class
End Namespace
// This example shows how to subscribe to changes of multiple items and obtain the item changed events by pulling them.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

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

namespace DocExamples.DataAccess._EasyDAClient
{
    partial class PullItemChanged
    {
        public static void MultipleItems()
        {
            // Instantiate the client object.
            // In order to use event pull, you must set a non-zero queue capacity upfront.
            var client = new EasyDAClient { PullItemChangedQueueCapacity = 1000 };

            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),
                    // Intentionally specifying an unknown item here, to demonstrate its behavior.
                    new DAItemGroupArguments("", "OPCLabs.KitServer.2", "SomeUnknownItem", 1000, null)
                });

            Console.WriteLine("Processing item changes for 1 minute...");
            int endTick = Environment.TickCount + 60 * 1000;
            do
            {
                EasyDAItemChangedEventArgs eventArgs = client.PullItemChanged(2 * 1000);
                if (!(eventArgs is null))
                    // Handle the notification event
                    if (eventArgs.Succeeded)
                        Console.WriteLine($"{eventArgs.Arguments.ItemDescriptor.ItemId}: {eventArgs.Vtq}");
                    else
                        Console.WriteLine($"{eventArgs.Arguments.ItemDescriptor.ItemId} *** Failure: {eventArgs.ErrorMessageBrief}");
            } while (Environment.TickCount < endTick);

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

            Console.WriteLine("Finished.");
        }
    }
}
# This example shows how to subscribe to changes of multiple items and obtain the item changed events by pulling them.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

#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
# In order to use event pull, you must set a non-zero queue capacity upfront.
$client.PullItemChangedQueueCapacity = 1000

Write-Host "Subscribing item changes..."
$handleArray = [OpcLabs.EasyOpc.DataAccess.IEasyDAClientExtension]::SubscribeMultipleItems($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)),
    # Intentionally specifying an unknown item here, to demonstrate its behavior.
    (New-Object DAItemGroupArguments("", "OPCLabs.KitServer.2", "SomeUnknownItem", 1000, $null))
    ))

Write-Host "Processing item changes for 1 minute..."
$stopwatch =  [System.Diagnostics.Stopwatch]::StartNew() 
while ($stopwatch.Elapsed.TotalSeconds -lt 60) {    
    $eventArgs = [IEasyDAClientExtension]::PullItemChanged($client, 2*1000)
    if ($eventArgs -ne $null) {
        # Handle the notification event
        if ($eventArgs.Succeeded) {
            Write-Host "$($eventArgs.Arguments.ItemDescriptor.ItemId): $($eventArgs.Vtq)"
        }
        else {
            Write-Host "$($eventArgs.Arguments.ItemDescriptor.ItemId) *** Failure: $($eventArgs.ErrorMessageBrief)"
        }
    }
}

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

Write-Host "Finished."

# This example shows how to subscribe to changes of multiple items and obtain the item changed events by pulling them.
#
# 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 .
# 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 *


# Instantiate the client object
client = EasyDAClient()
# In order to use event pull, you must set a non-zero queue capacity upfront.
client.PullItemChangedQueueCapacity = 1000

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', 'UnknownItem', 1000, None),
    ])

print('Processing item changes for 1 minute...')
endTime = time.time() + 60
while time.time() < endTime:
    eventArgs = IEasyDAClientExtension.PullItemChanged(client, 2*1000)
    if eventArgs is not None:
        # Handle the notification event
        if (eventArgs.Succeeded):
            print(eventArgs.Arguments.ItemDescriptor.ItemId, ': ', eventArgs.Vtq, sep='')
        else:
            print(eventArgs.Arguments.ItemDescriptor.ItemId, ' *** Failure: ', eventArgs.ErrorMessageBrief, sep='')

print('Unsubscribing item changes...')
client.UnsubscribeAllItems()

print('Finished.')

' This example shows how to subscribe to changes of multiple items and obtain the item changed events by pulling them.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.DataAccess.OperationModel

Namespace DataAccess._EasyDAClient
    Partial Friend Class PullItemChanged
        Public Shared Sub MultipleItems()
            ' Instantiate the client object.
            ' In order to use event pull, you must set a non-zero queue capacity upfront.
            Dim client = New EasyDAClient With {.PullItemChangedQueueCapacity = 1000}

            Console.WriteLine("Subscribing item changes...")
            ' Intentionally specifying an unknown item here, to demonstrate its behavior.
            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", "SomeUnknownItem", 1000, Nothing)
                })

            Console.WriteLine("Processing item changes for 1 minute...")
            Dim endTick As Integer = Environment.TickCount + 60 * 1000
            Do
                Dim eventArgs As EasyDAItemChangedEventArgs = client.PullItemChanged(2 * 1000)
                If Not eventArgs Is Nothing Then
                    ' Handle the notification event
                    If eventArgs.Succeeded Then
                        Console.WriteLine($"{eventArgs.Arguments.ItemDescriptor.ItemId}: {eventArgs.Vtq}")
                    Else
                        Console.WriteLine($"{eventArgs.Arguments.ItemDescriptor.ItemId} *** Failure: {eventArgs.ErrorMessageBrief}")
                    End If
                End If
            Loop While Environment.TickCount < endTick

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

            Console.WriteLine("Finished.")
        End Sub
    End Class
End Namespace
// This example shows how to subscribe to OPC XML-DA item changes and obtain the events by pulling them.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

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

namespace DocExamples.DataAccess.Xml
{
    class PullItemChanged
    {
        public static void Main1Xml()
        {
            // Instantiate the client object.
            // In order to use event pull, you must set a non-zero queue capacity upfront.
            var client = new EasyDAClient { PullItemChangedQueueCapacity = 1000 };

            Console.WriteLine("Subscribing item changes...");
            client.SubscribeItem(
                "http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx",
                "Dynamic/Analog Types/Int",
                1000,
                state: null);

            Console.WriteLine("Processing item changes for 1 minute...");
            int endTick = Environment.TickCount + 60 * 1000;
            do
            {
                EasyDAItemChangedEventArgs eventArgs = client.PullItemChanged(2 * 1000);
                if (!(eventArgs is null))
                    // Handle the notification event
                    Console.WriteLine(eventArgs);
            } while (Environment.TickCount < endTick);

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

            Console.WriteLine("Finished.");
        }
    }
}
' This example shows how to subscribe to OPC XML-DA item changes and obtain the events by pulling them.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.DataAccess.OperationModel

Namespace DataAccess.Xml
    Partial Friend Class PullItemChanged
        Public Shared Sub Main1Xml()
            ' In order to use event pull, you must set a non-zero queue capacity upfront.
            Dim client = New EasyDAClient() With {.PullItemChangedQueueCapacity = 1000}

            Console.WriteLine("Subscribing item changes...")
            client.SubscribeItem(
                    "http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx",
                    "Dynamic/Analog Types/Int",
                    1000,
                    state:=Nothing)

            Console.WriteLine("Processing item changes for 1 minute...")
            Dim endTick As Integer = Environment.TickCount + 60 * 1000
            Do
                Dim eventArgs As EasyDAItemChangedEventArgs = client.PullItemChanged(2 * 1000)
                If Not eventArgs Is Nothing Then
                    ' Handle the notification event
                    Console.WriteLine(eventArgs)
                End If
            Loop While Environment.TickCount < endTick

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

            Console.WriteLine("Finished.")
        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

See Also

Reference

IEasyDAClientExtension Class
IEasyDAClientExtension Members

 

 

Copyright © 2004-2024 CODE Consulting and Development, s.r.o., Plzen. All rights reserved.

Send Documentation Feedback. Technical Support