BrowseNotifiers(IEasyUAClient,UAEndpointDescriptor,UANodeDescriptor) Method

Browses the Notifiers in OPC server's address space. Starts from the specified node (or Notifiers folder), and returns information about child nodes found. Browses the Notifiers, specifying an endpoint descriptor, and a starting Node Id.

Syntax

[Extension()]
[ElementsNotNull()]
[NotNull()]
public static UANodeElementCollection BrowseNotifiers( 
   IEasyUAClient client,
   UAEndpointDescriptor endpointDescriptor,
   UANodeDescriptor nodeDescriptor
)

[Extension()]
[ElementsNotNull()]
[NotNull()]
public:
static UANodeElementCollection^ BrowseNotifiers( 
   IEasyUAClient^ client,
   UAEndpointDescriptor^ endpointDescriptor,
   UANodeDescriptor^ nodeDescriptor
)

'Declaration
 
<ExtensionAttribute()>
<ElementsNotNullAttribute()>
<NotNullAttribute()>
Public Overloads Shared Function BrowseNotifiers( _
   ByVal client As IEasyUAClient, _
   ByVal endpointDescriptor As UAEndpointDescriptor, _
   ByVal nodeDescriptor As UANodeDescriptor _
) As UANodeElementCollection

'Usage
 
Dim client As IEasyUAClient
Dim endpointDescriptor As UAEndpointDescriptor
Dim nodeDescriptor As UANodeDescriptor
Dim value As UANodeElementCollection
 
value = IEasyUAClientExtension.BrowseNotifiers(client, endpointDescriptor, nodeDescriptor)

Parameters

client: The client object that will perform the operation.
endpointDescriptor: Endpoint descriptor. Identifies the OPC-UA server.
nodeDescriptor: Node descriptor. Identifies the node in OPC server's address space.

Return Value

The method returns a node element collection, which contains OpcLabs.EasyOpc.UA.AddressSpace.UANodeElement values. Each element contains information about a particular node found.

Exceptions

Exception Description

Exception	Description
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.
OpcLabs.EasyOpc.UA.OperationModel.UAException	The OPC UA operation has failed. This operation exception in uniformly used to allow common handling of various kinds of errors. The System.Exception.InnerException always contains information about the actual error cause. This is an operation error that depends on factors external to your program, and thus cannot be always avoided. Your code must handle it appropriately.

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.

OpcLabs.EasyOpc.UA.OperationModel.UAException

The OPC UA operation has failed. This operation exception in uniformly used to allow common handling of various kinds of errors. The System.Exception.InnerException always contains information about the actual error cause.

This is an operation error that depends on factors external to your program, and thus cannot be always avoided. Your code must handle it appropriately.

Example

.NET

COM

// This example shows how to browse objects under the "Objects" node and display notifiers.

using System;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.AddressSpace;
using OpcLabs.EasyOpc.UA.AddressSpace.Standard;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples.AlarmsAndConditions
{
    class BrowseNotifiers
    {
        public static void Overload2()
        {
            // Start browsing from the "Objects" node.
            try
            {
                BrowseFrom(UAObjectIds.ObjectsFolder);
            }
            catch (UAException uaException)
            {
                Console.WriteLine($"*** Failure: {uaException.GetBaseException().Message}");
            }

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

        private static void BrowseFrom(UANodeDescriptor nodeDescriptor)
        {
            // Define which server we will work with.
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer";

            Console.WriteLine();
            Console.WriteLine();
            Console.WriteLine($"Parent node: {nodeDescriptor}");

            // Instantiate the client object.
            var client = new EasyUAClient();

            // Obtain notifiers.
            UANodeElementCollection notifierNodeElementCollection = client.BrowseNotifiers(
                endpointDescriptor, nodeDescriptor);

            // Display notifiers.
            if (notifierNodeElementCollection.Count != 0)
            {
                Console.WriteLine();
                Console.WriteLine("Notifiers:");
                foreach (UANodeElement notifierNodeElement in notifierNodeElementCollection)
                    Console.WriteLine(notifierNodeElement);
            }

            // Obtain objects.
            UANodeElementCollection objectNodeElementCollection = client.BrowseObjects(
                endpointDescriptor, nodeDescriptor);

            // Recurse.
            foreach (UANodeElement objectNodeElement in objectNodeElementCollection)
                BrowseFrom(objectNodeElement);
        }

        // Example output (truncated):
        //
        //
        //Parent node: ObjectsFolder
        //
        //
        //Parent node: Server
        //
        //Notifiers:
        //Green -> nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=0:/Green (Object)
        //Yellow -> nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=0:/Yellow (Object)
        //
        //
        //Parent node: Server_ServerCapabilities
        //...
    }
}

# This example shows how to browse objects under the "Objects" node and display notifiers.

#requires -Version 5.1
using namespace OpcLabs.EasyOpc.UA
using namespace OpcLabs.EasyOpc.UA.AddressSpace.Standard
using namespace OpcLabs.EasyOpc.UA.Navigation.Parsing;
using namespace OpcLabs.EasyOpc.UA.OperationModel


function BrowseNotifiersFrom([UANodeDescriptor]$nodeDescriptor) { 

    # Define which server we will work with.
    [UAEndpointDescriptor]$endpointDescriptor = "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer"

    Write-Host
    Write-Host
    Write-Host "Parent node: $($nodeDescriptor)"

    # Instantiate the client object.
    $client = New-Object EasyUAClient

    # Obtain event sources.
    $notifierNodeElementCollection = [IEasyUAClientExtension]::BrowseNotifiers($client,
        $endpointDescriptor, $nodeDescriptor)

    # Display event sources.
    if ($notifierNodeElementCollection.Count -ne 0) {
        Write-Host
        Write-Host "Notifiers:"
        foreach ($notifierNodeElement in $notifierNodeElementCollection) {
            Write-Host $notifierNodeElement
        }
    }

    # Obtain objects.
    $objectNodeElementCollection = [IEasyUAClientExtension]::BrowseObjects($client,
        $endpointDescriptor, $nodeDescriptor)

    # Recurse.
    foreach ($objectNodeElement in $objectNodeElementCollection) {
        BrowseNotifiersFrom($objectNodeElement)
    }
}


# The path below assumes that the current directory is [ProductDir]/Examples-NET/PowerShell/Windows .
Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcUA.dll"
Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcUAComponents.dll"

# Start browsing from the "Objects" node.
try {
    [UANodeDescriptor]$startingNodeDescriptor = [UAObjectIds]::ObjectsFolder
    BrowseNotifiersFrom $startingNodeDescriptor
}
catch [UAException] {
    Write-Host "*** Failure: $($PSItem.Exception.GetBaseException().Message)"
    return
}

Write-Host
Write-Host "Finished."


# Example output (truncated):
#
#
#Parent node: ObjectsFolder
#
#
#Parent node: Server
#
#Notifiers:
#Green -> nsu=http:#opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=0:/Green (Object)
#Yellow -> nsu=http:#opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=0:/Yellow (Object)
#
#
#Parent node: Server_ServerCapabilities
#...

# This example shows how to browse objects under the "Objects" node and display notifiers.

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

# Import .NET namespaces.
from OpcLabs.EasyOpc.UA import *
from OpcLabs.EasyOpc.UA.AddressSpace import *
from OpcLabs.EasyOpc.UA.AddressSpace.Standard import *
from OpcLabs.EasyOpc.UA.OperationModel import *


# Define which server we will work with.
endpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer')


def browseFrom(nodeDescriptor):
    global endpointDescriptor

    print()
    print()
    print('Parent node: ', nodeDescriptor, sep='')

    # Instantiate the client object.
    client = EasyUAClient()

    # Obtain notifiers.
    notifierNodeElementCollection = IEasyUAClientExtension.BrowseNotifiers(client, endpointDescriptor, nodeDescriptor)

    # Display notifiers.
    if notifierNodeElementCollection.Count != 0:
        print('')
        print('Notifiers:')
        for notifierNodeElement in notifierNodeElementCollection:
            print(notifierNodeElement)

    # Obtain objects.
    objectNodeElementCollection = IEasyUAClientExtension.BrowseObjects(client,
                                                                       endpointDescriptor,
                                                                       nodeDescriptor)

    # Recurse.
    for objectNodeElement in objectNodeElementCollection:
        browseFrom(objectNodeElement.ToUANodeDescriptor())


# Start browsing from the "Objects" node.
try:
    browseFrom(UANodeDescriptor(UAObjectIds.ObjectsFolder))
except UAException as uaException:
    print('*** Failure: ' + uaException.GetBaseException().Message)
    exit()

print()
print('Finished.')

' This example shows how to browse objects under the "Objects" node and display notifiers.

Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.AddressSpace
Imports OpcLabs.EasyOpc.UA.AddressSpace.Standard
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace AlarmsAndConditions
    Friend Class BrowseNotifiers
        Public Shared Sub Overload2()

            ' Start browsing from the "Objects" node
            Try
                BrowseFrom(UAObjectIds.ObjectsFolder)
            Catch uaException As UAException
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException.Message)
            End Try
        End Sub

        Private Shared Sub BrowseFrom(nodeDescriptor As UANodeDescriptor)

            Console.WriteLine()
            Console.WriteLine()
            Console.WriteLine("Parent node: {0}", nodeDescriptor)

            ' Instantiate the client object
            Dim client = New EasyUAClient()

            ' Obtain notifiers
            Dim notifierNodeElementCollection As UANodeElementCollection = client.BrowseNotifiers( _
                "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer", _
                nodeDescriptor)

            ' Display notifiers
            Console.WriteLine()
            Console.WriteLine("Notifiers:")
            For Each notifierNodeElement As UANodeElement In notifierNodeElementCollection
                Console.WriteLine(notifierNodeElement)
            Next notifierNodeElement

            ' Obtain objects
            Dim objectNodeElementCollection = client.BrowseObjects( _
                "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer", _
                nodeDescriptor)

            ' Recurse
            For Each objectNodeElement As UANodeElement In objectNodeElementCollection
                BrowseFrom(objectNodeElement)
            Next objectNodeElement
        End Sub
    End Class
End Namespace

// This example shows how to browse objects under the "Objects" node and display notifiers.

class procedure BrowseNotifiers.Main;
var
  ObjectNodeId: _UANodeId;
begin
  ObjectNodeId := CoUANodeId.Create;
  ObjectNodeId.StandardName := 'Objects';
  try
    BrowseFrom(ObjectNodeId);
  except
    on E: EOleException do
    begin
      WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message]));
      Exit;
    end;
  end;
end;

class procedure BrowseNotifiers.BrowseFrom(NodeId: _UANodeId);
var
  Client: OpcLabs_EasyOpcUA_TLB._EasyUAClient;
  Count: Cardinal;
  Element: OleVariant;
  EndpointDescriptor: string;
  NotifierNodeElement: _UANodeElement;
  NotifierNodeElementEnumerator: IEnumVariant;
  NotifierNodeElements: _UANodeElementCollection;
  ObjectNodeElement: _UANodeElement;
  ObjectNodeElementEnumerator: IEnumVariant;
  ObjectNodeElements: _UANodeElementCollection;
begin
  EndpointDescriptor := 'opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer';

  WriteLn;
  WriteLn;
  WriteLn('Parent node: ', NodeId.ToString);

  // Instantiate the client object
  Client := CoEasyUAClient.Create;

  // Obtain notifiers
  NotifierNodeElements := Client.BrowseNotifiers(EndpointDescriptor, NodeId.ExpandedText);

  // Display notifires
  if NotifierNodeElements.Count <> 0 then
  begin
    WriteLn;
    WriteLn('Notifiers:');
    NotifierNodeElementEnumerator := NotifierNodeElements.GetEnumerator;
    while (NotifierNodeElementEnumerator.Next(1, Element, Count) = S_OK) do
    begin
      NotifierNodeElement := IUnknown(Element) as _UANodeElement;
      WriteLn(NotifierNodeElement.ToString);
    end;
  end;

  // Obtain objects
  ObjectNodeElements := Client.BrowseObjects(EndpointDescriptor, NodeId.ExpandedText);

  // Recurse
  ObjectNodeElementEnumerator := ObjectNodeElements.GetEnumerator;
  while (ObjectNodeElementEnumerator.Next(1, Element, Count) = S_OK) do
  begin
    ObjectNodeElement := IUnknown(Element) as _UANodeElement;
    BrowseFrom(ObjectNodeElement.NodeId);
  end;
end;

// Example output (truncated):
//
//
//Parent node: ObjectsFolder
//
//
//Parent node: Server
//
//Notifiers:
//Green -> nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=0:/Green (Object)
//Yellow -> nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=0:/Yellow (Object)
//
//
//Parent node: Server_ServerCapabilities
//...

// This example shows how to browse objects under the "Objects" node and display notifiers.


// Start browsing from the "Objects" node
$ObjectNodeId = new COM("OpcLabs.EasyOpc.UA.AddressSpace.UANodeId");
$ObjectNodeId->StandardName = "Objects";
try
{
    BrowseFrom($ObjectNodeId);
}
catch (com_exception $e)
{
    printf("*** Failure: %s\n", $e->getMessage());
    exit();
}

function BrowseFrom($NodeId) {
    $EndpointDescriptor = "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer";

    printf("\n");
    printf("\n");
    printf("Parent node: %s\n", $NodeId);

    // Instantiate the client object
    $Client = new COM("OpcLabs.EasyOpc.UA.EasyUAClient");

    // Obtain notifiers
    $NotifierNodeElements = $Client->BrowseNotifiers($EndpointDescriptor, $NodeId->ExpandedText);

    // Display notifires
    if ($NotifierNodeElements->Count != 0) {
        printf("\n");
        printf("Notifiers:\n");
        foreach ($NotifierNodeElements as $NotifierNodeElement)
        {
             printf("%s\n", $NotifierNodeElement);
        }
    }

    // Obtain objects
    $ObjectNodeElements = $Client->BrowseObjects($EndpointDescriptor, $NodeId->ExpandedText);

    // Recurse
    foreach ($ObjectNodeElements as $ObjectNodeElement)
    {
         BrowseFrom($ObjectNodeElement->NodeId);
    }
}

// Example output (truncated):
//
//
//Parent node: ObjectsFolder
//
//
//Parent node: Server
//
//Notifiers:
//Green -> nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=0:/Green (Object)
//Yellow -> nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=0:/Yellow (Object)
//
//
//Parent node: Server_ServerCapabilities
//...

Rem This example shows how to browse objects under the "Objects" node and display notifiers.

Option Explicit

' Start browsing from the "Objects" node
Dim ObjectsNodeId: Set ObjectsNodeId = CreateObject("OpcLabs.EasyOpc.UA.AddressSpace.UANodeId")
ObjectsNodeId.StandardName = "Objects"
On Error Resume Next
BrowseFrom ObjectsNodeId
If Err.Number <> 0 Then
    WScript.Echo "*** Failure: " & Err.Source & ": " & Err.Description
    WScript.Quit
End If
On Error Goto 0



Sub BrowseFrom(NodeId)
    Dim endpointDescriptor
    endpointDescriptor = "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer"

    WScript.Echo 
    WScript.Echo 
    WScript.Echo "Parent node: " & NodeId

    ' Instantiate the client object
    Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.UA.EasyUAClient")

    ' Obtain notifiers
    Dim NotifierNodeElementCollection: Set NotifierNodeElementCollection = Client.BrowseNotifiers( _
        endpointDescriptor, NodeId.ExpandedText)

    ' Display notifiers
    If NotifierNodeElementCollection.Count <> 0 Then
        WScript.Echo 
        WScript.Echo "Notifiers:"
        Dim NotifierNodeElement: For Each NotifierNodeElement In NotifierNodeElementCollection
            WScript.Echo NotifierNodeElement
        Next
    End If
    
    ' Obtain objects
    Dim ObjectNodeElementCollection: Set ObjectNodeElementCollection = Client.BrowseObjects( _
        endpointDescriptor, NodeId.ExpandedText)

    ' Recurse
    Dim ObjectNodeElement: For Each ObjectNodeElement In ObjectNodeElementCollection
        BrowseFrom ObjectNodeElement.NodeId
    Next
End Sub



' Example output (truncated):
'
'
'Parent node: ObjectsFolder
'
'
'Parent node: Server
'
'Notifiers:
'Green -> nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=0:/Green (Object)
'Yellow -> nsu=http://opcfoundation.org/Quickstarts/AlarmCondition ;ns=2;s=0:/Yellow (Object)
'
'
'Parent node: Server_ServerCapabilities
'...

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

IEasyUAClientExtension Class
IEasyUAClientExtension Members
Overload List

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