UnsubscribeEvents Method (

Unsubscribe from particular OPC event notifications.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
Sub UnsubscribeEvents( _
   ByVal handle As Integer _
)

'Usage
 
Dim instance As _EasyAEClient
Dim handle As Integer
 
instance.UnsubscribeEvents(handle)

void UnsubscribeEvents( 
   int handle
)

void UnsubscribeEvents( 
   int handle
)

Parameters

handle: Event subscription handle as returned by the SubscribeEvents method

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.

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.

Remarks

The event subscription handle becomes invalid after this method is called.

This member or type is for use from COM. It is not meant to be used from .NET or Python. Refer to the corresponding .NET member or type instead, if you are developing in .NET or Python.

Example

REM This example shows how to subscribe to events and display the event message with each notification. It also shows how to
REM unsubscribe afterwards.
REM
REM Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
REM OPC client and subscriber examples in Visual Basic on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VB .
REM Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
REM a commercial license in order to use Online Forums, and we reply to every post.

Private Sub SubscribeEvents_Main_Command_Click()
    OutputText = ""
    
    Dim serverDescriptor As New serverDescriptor
    serverDescriptor.ServerClass = "OPCLabs.KitEventServer.2"
    
    ' Instantiate the client object and hook events
    Set Client1 = New EasyAEClient
    
    OutputText = OutputText & "Subscribing..." & vbCrLf
    Dim subscriptionParameters As New AESubscriptionParameters
    subscriptionParameters.notificationRate = 1000
    Dim handle
    Dim state
    handle = Client1.SubscribeEvents(serverDescriptor, subscriptionParameters, True, state)

    OutputText = OutputText & "Processing event notifications for 1 minute..." & vbCrLf
    Pause 60000

    OutputText = OutputText & "Unsubscribing events..." & vbCrLf
    Client1.UnsubscribeEvents handle

    OutputText = OutputText & "Waiting for 5 seconds..." & vbCrLf
    Pause 5000

    OutputText = OutputText & "Finished." & vbCrLf

    Set Client1 = Nothing
End Sub

Private Sub Client1_OnNotification(ByVal sender As Variant, ByVal eventArgs As EasyAENotificationEventArgs)
    If Not eventArgs.Succeeded Then
        OutputText = OutputText & eventArgs.ErrorMessageBrief & vbCrLf
        Exit Sub
    End If
    If Not eventArgs.EventData Is Nothing Then
        OutputText = OutputText & eventArgs.EventData.Message & vbCrLf
    End If
End Sub

Rem This example shows how to unsubscribe from specific event notifications.
Rem
Rem Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
Rem OPC client and subscriber examples in VBScript on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBScript .
Rem Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
Rem a commercial license in order to use Online Forums, and we reply to every post.

Option Explicit

Dim ServerDescriptor: Set ServerDescriptor = CreateObject("OpcLabs.EasyOpc.ServerDescriptor")
ServerDescriptor.ServerClass = "OPCLabs.KitEventServer.2"

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

WScript.Echo "Subscribing..."
Dim SubscriptionParameters: Set SubscriptionParameters = CreateObject("OpcLabs.EasyOpc.AlarmsAndEvents.AESubscriptionParameters")
SubscriptionParameters.NotificationRate = 1000
Dim handle: handle = Client.SubscribeEvents(ServerDescriptor, SubscriptionParameters, True, Nothing)

WScript.Echo "Waiting for 10 seconds..."
WScript.Sleep 10*1000

WScript.Echo "Unsubscribing..."
Client.UnsubscribeEvents handle

WScript.Echo "Waiting for 10 seconds..."
WScript.Sleep 10*1000



Rem Notification event handler
Sub Client_Notification(Sender, e)
    If Not (e.Succeeded) Then
        WScript.Echo "*** Failure: " & e.ErrorMessageBrief
        Exit Sub
    End If

    If Not e.EventData Is Nothing Then WScript.Echo e.EventData.Message
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

_EasyAEClient Interface
_EasyAEClient Members

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Missing some example? Ask us for it on our Online Forums! You do not have to own a commercial license in order to use Online Forums, and we reply to every post.