Changes parameters of an event subscription. Specify new notification rate. There will be no filtering, and the subscription will be activated.
Syntax
Parameters
- client
- The client object that will perform the operation.
This is typically the EasyAEClient object.
The value of this parameter cannot be null
(Nothing
in Visual Basic).
- handle
- Event subscription handle as returned by the SubscribeEvents method
- notificationRate
- The requested notification rate. The notification rate is in milliseconds and tells the server how often to send event notifications. This is a minimum time - do not send event notifications any faster that this UNLESS the buffer size is reached. A value of 0 for notification rate means that the server should send event notifications as soon as it gets them. This parameter is used to improve communications efficiency between client and server. This parameter is a recommendation from the client, and the server is allowed to ignore the parameter.
Exceptions
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.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
// This example shows how to subscribe to events and later change the notification rate.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-CSharp .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.
using System;
using System.Threading;
using OpcLabs.EasyOpc.AlarmsAndEvents;
using OpcLabs.EasyOpc.AlarmsAndEvents.OperationModel;
namespace DocExamples.AlarmsAndEvents._EasyAEClient
{
class ChangeEventSubscription
{
public static void Main1()
{
// Instantiate the client object.
using (var client = new EasyAEClient())
{
var eventHandler = new EasyAENotificationEventHandler(client_Notification);
client.Notification += eventHandler;
Console.WriteLine("Subscribing...");
int handle = client.SubscribeEvents("", "OPCLabs.KitEventServer.2", 500);
Console.WriteLine("Waiting for 10 seconds...");
Thread.Sleep(10 * 1000);
Console.WriteLine("Changing subscription...");
client.ChangeEventSubscription(handle, 5 * 1000);
Console.WriteLine("Waiting for 50 seconds...");
Thread.Sleep(50 * 1000);
client.UnsubscribeEvents(handle);
}
}
// Notification event handler
static void client_Notification(object sender, EasyAENotificationEventArgs e)
{
if (!e.Succeeded)
{
Console.WriteLine("*** Failure: {0}", e.ErrorMessageBrief);
return;
}
if (!(e.EventData is null))
Console.WriteLine(e.EventData.Message);
}
}
}
' This example shows how to subscribe to events and later change the notification rate.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET .
' Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
' a commercial license in order to use Online Forums, and we reply to every post.
Imports System.Threading
Imports OpcLabs.EasyOpc.AlarmsAndEvents
Imports OpcLabs.EasyOpc.AlarmsAndEvents.OperationModel
Namespace AlarmsAndEvents._EasyAEClient
Friend Class ChangeEventSubscription
Public Shared Sub Main1()
Using client = New EasyAEClient()
Dim eventHandler = New EasyAENotificationEventHandler(AddressOf client_Notification)
AddHandler client.Notification, eventHandler
Console.WriteLine("Subscribing...")
Dim handle As Integer = client.SubscribeEvents("", "OPCLabs.KitEventServer.2", 500)
Console.WriteLine("Waiting for 10 seconds...")
Thread.Sleep(10 * 1000)
Console.WriteLine("Changing subscription...")
client.ChangeEventSubscription(handle, 5 * 1000)
Console.WriteLine("Waiting for 50 seconds...")
Thread.Sleep(50 * 1000)
client.UnsubscribeEvents(handle)
End Using
End Sub
' Notification event handler
Private Shared Sub client_Notification(ByVal sender As Object, ByVal e As EasyAENotificationEventArgs)
If Not e.Succeeded Then
Console.WriteLine("*** Failure: {0}", e.ErrorMessageBrief)
Exit Sub
End If
If e.EventData IsNot Nothing Then
Console.WriteLine(e.EventData.Message)
End If
End Sub
End Class
End Namespace
# This example shows how to subscribe to events and later change the notification rate.
#
# 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 .
# Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
# a commercial license in order to use Online Forums, and we reply to every post.
# 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.AlarmsAndEvents import *
# Notification event handler
def notification(sender, e):
if not e.Succeeded:
print('*** Failure: ', e.ErrorMessageBrief, sep='')
return
else:
if e.EventData is not None:
print(e.EventData.Message)
# Instantiate the client object
client = EasyAEClient()
client.Notification += notification
print('Subscribing events...')
handle = IEasyAEClientExtension.SubscribeEvents(client, '', 'OPCLabs.KitEventServer.2', 500)
print('Waiting for 10 seconds...')
time.sleep(10)
print('Changing event subscription...')
IEasyAEClientExtension.ChangeEventSubscription(client, handle, 5*1000)
print('Waiting for 50 seconds...')
time.sleep(50)
print('Unsubscribing events...')
client.UnsubscribeAllEvents()
client.Notification -= notification
print('Finished.')
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