PullNotification Method (IEasyAEClientExtension)

Attempts to pull an OPC event subscribed to by the SubscribeEvents method. Returns refresh or standard event notifications.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<ExtensionAttribute()>
<CanBeNullAttribute()>
Public Shared Function PullNotification( _
   ByVal client As IEasyAEClient, _
   ByVal millisecondsTimeout As Integer _
) As EasyAENotificationEventArgs

'Usage
 
Dim client As IEasyAEClient
Dim millisecondsTimeout As Integer
Dim value As EasyAENotificationEventArgs
 
value = IEasyAEClientExtension.PullNotification(client, millisecondsTimeout)

[Extension()]
[CanBeNull()]
public static EasyAENotificationEventArgs PullNotification( 
   IEasyAEClient client,
   int millisecondsTimeout
)

[Extension()]
[CanBeNull()]
public:
static EasyAENotificationEventArgs^ PullNotification( 
   IEasyAEClient^ 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

Exception	Description
System.ArgumentOutOfRangeException	The value of an argument is outside the allowable range of values as defined by the invoked method.
System.ArgumentNullException	A `null` reference (`Nothing` in Visual Basic) is passed to a method that does not accept it as a valid argument.

Example

CSharp
PowerShell
PHP
Visual Basic (VB 6.0)
VB.NET

// This example shows how to subscribe to events and obtain the notification events by pulling them.

using System;
using OpcLabs.EasyOpc.AlarmsAndEvents;
using OpcLabs.EasyOpc.AlarmsAndEvents.OperationModel;

namespace DocExamples.AlarmsAndEvents._EasyAEClient
{
    class PullNotification
    {
        public static void Main1()
        {
            // Instantiate the client object.
            // In order to use event pull, you must set a non-zero queue capacity upfront.
            using (var client = new EasyAEClient { PullNotificationQueueCapacity = 1000 })
            {
                Console.WriteLine("Subscribing events...");
                int handle = client.SubscribeEvents("", "OPCLabs.KitEventServer.2", 1000);

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

                Console.WriteLine("Unsubscribing events...");
                client.UnsubscribeEvents(handle);

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

# This example shows how to subscribe to events and obtain the notification events by pulling them.

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

# The path below assumes that the current directory is [ProductDir]/Examples-NET/PowerShell/Windows .
Add-Type -Path "../../../Assemblies/net47/OpcLabs.EasyOpcClassic.dll"

# Instantiate the client object.
$client = New-Object EasyAEClient
# In order to use event pull, you must set a non-zero queue capacity upfront.
$client.PullNotificationQueueCapacity = 1000

Write-Host "Subscribing events..."
$handle = [OpcLabs.EasyOpc.AlarmsAndEvents.IEasyAEClientExtension]::SubscribeEvents($client, 
    "", "OPCLabs.KitEventServer.2", 1000)

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

Write-Host "Unsubscribing events..."
$client.UnsubscribeEvents($handle)

Write-Host "Finished."

// This example shows how to subscribe to events and obtain the notification events by pulling them.

$ServerDescriptor = new COM("OpcLabs.EasyOpc.ServerDescriptor");
$ServerDescriptor->ServerClass = "OPCLabs.KitEventServer.2";

$Client = new COM("OpcLabs.EasyOpc.AlarmsAndEvents.EasyAEClient");
// In order to use event pull, you must set a non-zero queue capacity upfront.
$Client->PullNotificationQueueCapacity = 1000;

print "Subscribing events...\n";
$SubscriptionParameters = new COM("OpcLabs.EasyOpc.AlarmsAndEvents.AESubscriptionParameters");
$SubscriptionParameters->NotificationRate = 1000;
$handle = $Client->SubscribeEvents($ServerDescriptor, $SubscriptionParameters, TRUE, NULL);

print "Processing event notifications for 1 minute...\n";
$endTime = time() + 60;
do {
    $EventArgs = $Client->PullNotification(2*1000);
    if (!is_null($EventArgs)) {
        // Handle the notification event
        print $EventArgs->ToString();
        print "\n";
    }
} while (time() < $endTime);

print "Unsubscribing events...\n";
$Client->UnsubscribeEvents($handle);

print "Finished.\n";

Rem This example shows how to subscribe to events and obtain the notification events by pulling them.

Private Sub PullNotification_Main_Command_Click()
    OutputText = ""
    
    Dim eventArgs As EasyAENotificationEventArgs
    
    Dim serverDescriptor As New serverDescriptor
    serverDescriptor.ServerClass = "OPCLabs.KitEventServer.2"
        
    ' Instantiate the client object
    Dim client As New EasyAEClient
    
    ' In order to use event pull, you must set a non-zero queue capacity upfront.
    client.PullNotificationQueueCapacity = 1000
    
    OutputText = OutputText & "Subscribing events..." & vbCrLf
    Dim subscriptionParameters As New AESubscriptionParameters
    subscriptionParameters.notificationRate = 1000
    Dim handle
    Dim state
    handle = client.SubscribeEvents(serverDescriptor, subscriptionParameters, True, state)

    OutputText = OutputText & "Processing event notifications for 1 minute..." & vbCrLf
    Dim endTick As Long
    endTick = GetTickCount + 60000
    While GetTickCount < endTick
        Set eventArgs = client.PullNotification(2 * 1000)
        If Not eventArgs Is Nothing Then
            ' Handle the notification event
            OutputText = OutputText & eventArgs & vbCrLf
        End If
    Wend
    
    OutputText = OutputText & "Unsubscribing events..." & vbCrLf
    client.UnsubscribeEvents handle

    OutputText = OutputText & "Finished." & vbCrLf

End Sub

' This example shows how to subscribe to events and obtain the notification events by pulling them.

Imports OpcLabs.EasyOpc.AlarmsAndEvents
Imports OpcLabs.EasyOpc.AlarmsAndEvents.OperationModel

Namespace DocExamples.AlarmsAndEvents._EasyAEClient
    Partial Friend Class PullNotification
        Public Shared Sub Main1()
            Using client = New EasyAEClient()
                ' In order to use event pull, you must set a non-zero queue capacity upfront.
                client.PullNotificationQueueCapacity = 1000

                Console.WriteLine("Subscribing events...")
                Dim handle As Integer = client.SubscribeEvents("", "OPCLabs.KitEventServer.2", 1000)

                Console.WriteLine("Processing event notifications for 1 minute...")
                Dim endTick As Integer = Environment.TickCount + 60 * 1000
                Do
                    Dim eventArgs As EasyAENotificationEventArgs = client.PullNotification(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 events...")
                client.UnsubscribeEvents(handle)
            End Using

            Console.WriteLine("Finished.")
        End Sub
    End Class
End Namespace

Requirements

Target Platforms: .NET Framework: Windows 10 (selected versions), Windows 11 (selected versions), Windows Server 2012, Windows Server 2016; .NET Core, .NET 5, .NET 6: Linux, macOS, Microsoft Windows

Reference

IEasyAEClientExtension Class
IEasyAEClientExtension Members