BrowseDataVariables(IEasyUAClient,UAEndpointDescriptor,UANodeDescriptor) Method

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

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<ExtensionAttribute()>
<ElementsNotNullAttribute()>
<NotNullAttribute()>
Public Overloads Shared Function BrowseDataVariables( _
   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.BrowseDataVariables(client, endpointDescriptor, nodeDescriptor)

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

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

// This example shows how to obtain data variables under the "Server" node in the address space.

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

namespace UADocExamples._EasyUAClient
{
    class BrowseDataVariables
    {
        public static void Overload2()
        {
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";
            // or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            // or "https://opcua.demo-this.com:51212/UA/SampleServer/"

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

            // Obtain data variables under "Server" node.
            UANodeElementCollection nodeElementCollection;
            try
            {
                nodeElementCollection = client.BrowseDataVariables(endpointDescriptor, UAObjectIds.Server);
            }
            catch (UAException uaException)
            {
                Console.WriteLine($"*** Failure: {uaException.GetBaseException().Message}");
                return;
            }

            // Display results
            foreach (UANodeElement nodeElement in nodeElementCollection)
            {
                Console.WriteLine();
                Console.WriteLine($"nodeElement.DisplayName: {nodeElement.DisplayName}");
                Console.WriteLine($"nodeElement.NodeId: {nodeElement.NodeId}");
                Console.WriteLine($"nodeElement.NodeId.ExpandedText: {nodeElement.NodeId.ExpandedText}");
            }
        }

        // Example output:
        //
        //nodeElement.DisplayName: ServerStatus            
        //nodeElement.NodeId: Server_ServerStatus
        //nodeElement.NodeId.ExpandedText: nsu=http://opcfoundation.org/UA/ ;i=2256
    }
}

# This example shows how to obtain data variables under the "Server" node in the address space.

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

# 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"

[UAEndpointDescriptor]$endpointDescriptor =
    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
# or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
# or "https://opcua.demo-this.com:51212/UA/SampleServer/"

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

# Obtain data variables under "Server" node.
try {
    $nodeElementCollection = [IEasyUAClientExtension]::BrowseDataVariables($client, 
        $endpointDescriptor, [UAObjectIds]::Server)
}
catch [UAException] {
    Write-Host "*** Failure: $($PSItem.Exception.GetBaseException().Message)"
    return
}

# Display results
foreach ($nodeElement in $nodeElementCollection) {
    Write-Host
    Write-Host "nodeElement.DisplayName: $($nodeElement.DisplayName)"
    Write-Host "nodeElement.NodeId: $($nodeElement.NodeId)"
    Write-Host "nodeElement.NodeId.ExpandedText: $($nodeElement.NodeId.ExpandedText)"
}


# Example output:
#
#nodeElement.DisplayName: ServerStatus            
#nodeElement.NodeId: Server_ServerStatus
#nodeElement.NodeId.ExpandedText: nsu=http://opcfoundation.org/UA/ ;i=2256

# This example shows how to obtain data variables under the "Server" node in the address space.

# 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 *


endpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:51210/UA/SampleServer')
# or 'http://opcua.demo-this.com:51211/UA/SampleServer' (currently not supported)
# or 'https://opcua.demo-this.com:51212/UA/SampleServer/'

# Instantiate the client object.
client = EasyUAClient()

# Obtain data variables under "Server" node.
try:
    nodeElementCollection = IEasyUAClientExtension.BrowseDataVariables(client,
                                                                       endpointDescriptor,
                                                                       UANodeDescriptor(UAObjectIds.Server))
except UAException as uaException:
    print('*** Failure: ' + uaException.GetBaseException().Message)
    exit()

# Display results.
for nodeElement in nodeElementCollection:
    print()
    print('nodeElement.DisplayName: ', nodeElement.DisplayName, sep='')
    print('nodeElement.NodeId: ', nodeElement.NodeId, sep='')
    print('nodeElement.NodeId.ExpandedText: ', nodeElement.NodeId.ExpandedText, sep='')

print()
print('Finished.')

' This example shows how to obtain data variables under the "Server" node in the address space.

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

Namespace _EasyUAClient
    Friend Class BrowseDataVariables
        Public Shared Sub Overload2()

            ' Define which server we will work with.
            Dim endpointDescriptor As UAEndpointDescriptor =
                    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
            ' or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            ' or "https://opcua.demo-this.com:51212/UA/SampleServer/"

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

            ' Obtain variables under "Server" node
            Dim nodeElementCollection As UANodeElementCollection
            Try
                nodeElementCollection = client.BrowseDataVariables(endpointDescriptor, UAObjectIds.Server)
            Catch uaException As UAException
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException.Message)
                Exit Sub
            End Try

            ' Display results
            For Each nodeElement As UANodeElement In nodeElementCollection
                Console.WriteLine()
                Console.WriteLine("nodeElement.NodeId: {0}", nodeElement.NodeId)
                Console.WriteLine("nodeElement.DisplayName: {0}", nodeElement.DisplayName)
            Next nodeElement

            ' Example output:
            '
            'nodeElement.NodeId: nsu=http://opcfoundation.org/UA/;i=2256
            'nodeElement.DisplayName: ServerStatus            
        End Sub
    End Class
End Namespace

Object Pascal
PHP
Visual Basic (VB 6.0)
VBScript

// This example shows how to obtain data variables under the "Server" node
// in the address space.

class procedure BrowseDataVariables.Main;
var
  Client: OpcLabs_EasyOpcUA_TLB._EasyUAClient;
  Count: Cardinal;
  Element: OleVariant;
  EndpointDescriptor: string;
  NodeElement: _UANodeElement;
  NodeElementEnumerator: IEnumVariant;
  NodeElements: _UANodeElementCollection;
  ServerNodeId: _UANodeId;
begin
  EndpointDescriptor := 
    //'http://opcua.demo-this.com:51211/UA/SampleServer';
    //'https://opcua.demo-this.com:51212/UA/SampleServer/';
    'opc.tcp://opcua.demo-this.com:51210/UA/SampleServer';

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

  // Obtain variables under "Server" node
  ServerNodeId := CoUANodeId.Create;
  ServerNodeId.StandardName := 'Server';
  try
    NodeElements := Client.BrowseDataVariables(EndpointDescriptor, ServerNodeId.ExpandedText);
  except
    on E: EOleException do
    begin
      WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message]));
      Exit;
    end;
  end;

  // Display results
  NodeElementEnumerator := NodeElements.GetEnumerator;
  while (NodeElementEnumerator.Next(1, Element, Count) = S_OK) do
  begin
    NodeElement := IUnknown(Element) as _UANodeElement;
    WriteLn;
    WriteLn('nodeElement.NodeId: ', NodeElement.NodeId.ToString);
    WriteLn('nodeElement.NodeId.ExpandedText: ', NodeElement.NodeId.ExpandedText);
    WriteLn('nodeElement.DisplayName: ', NodeElement.DisplayName);
  end;

  // Example output:
  //
  //nodeElement.NodeId: Server_ServerStatus
  //nodeElement.NodeId.ExpandedText: nsu=http://opcfoundation.org/UA/ ;i=2256
  //nodeElement.DisplayName: ServerStatus
end;

// This example shows how to obtain data variables under the "Server" node
// in the address space.

$EndpointDescriptor = new COM("OpcLabs.EasyOpc.UA.UAEndpointDescriptor");
$EndpointDescriptor->UrlString = 
    //"http://opcua.demo-this.com:51211/UA/SampleServer";
    //"https://opcua.demo-this.com:51212/UA/SampleServer/";
    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";

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

// Obtain variables under "Server" node
$ServerNodeId = new COM("OpcLabs.EasyOpc.UA.AddressSpace.UANodeId");
$ServerNodeId->StandardName = "Server";

try
{
    $NodeElements = $Client->BrowseDataVariables($EndpointDescriptor, $ServerNodeId->ExpandedText);
}
catch (com_exception $e)
{
    printf("*** Failure: %s\n", $e->getMessage());
    exit();
}

// Display results
foreach ($NodeElements as $NodeElement)
{
    printf("\n");
    printf("nodeElement.NodeId: %s\n", $NodeElement->NodeId);
    printf("nodeElement.NodeId.ExpandedText: %s\n", $NodeElement->NodeId->ExpandedText);
    printf("nodeElement.DisplayName: %s\n", $NodeElement->DisplayName);
}

// Example output:
//
//nodeElement.NodeId: Server_ServerStatus
//nodeElement.NodeId.ExpandedText: nsu=http://opcfoundation.org/UA/ ;i=2256
//nodeElement.DisplayName: ServerStatus

Rem This example shows how to obtain data variables under the "Server" node
Rem in the address space.

Public Sub BrowseDataVariables_Main_Command_Click()
    OutputText = ""

    Dim endpointDescriptor As String
    'endpointDescriptor = "http://opcua.demo-this.com:51211/UA/SampleServer"
    'endpointDescriptor = "https://opcua.demo-this.com:51212/UA/SampleServer/"
    endpointDescriptor = "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"

    ' Instantiate the client object
    Dim Client As New EasyUAClient

    ' Obtain variables under "Server" node
    Dim serverNodeId As New UANodeId
    serverNodeId.StandardName = "Server"
    
    On Error Resume Next
    Dim NodeElements As UANodeElementCollection
    Set NodeElements = Client.BrowseDataVariables(endpointDescriptor, serverNodeId.expandedText)
    If Err.Number <> 0 Then
        OutputText = OutputText & "*** Failure: " & Err.Source & ": " & Err.Description & vbCrLf
        Exit Sub
    End If
    On Error GoTo 0

    ' Display results
    Dim NodeElement: For Each NodeElement In NodeElements
        OutputText = OutputText & vbCrLf
        OutputText = OutputText & "nodeElement.NodeId: " & NodeElement.NodeId & vbCrLf
        OutputText = OutputText & "nodeElement.NodeId.ExpandedText: " & NodeElement.NodeId.expandedText & vbCrLf
        OutputText = OutputText & "nodeElement.DisplayName: " & NodeElement.DisplayName & vbCrLf
    Next
    
    ' Example output:
    '
    'nodeElement.NodeId: Server_ServerStatus
    'nodeElement.NodeId.ExpandedText: nsu=http://opcfoundation.org/UA/ ;i=2256
    'nodeElement.DisplayName: ServerStatus
End Sub

Rem This example shows how to obtain data variables under the "Server" node in the address space.

Option Explicit

Dim endpointDescriptor: endpointDescriptor = _
    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
    '"http://opcua.demo-this.com:51211/UA/SampleServer"  
    '"https://opcua.demo-this.com:51212/UA/SampleServer/"

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

' Obtain variables under "Server" node
Dim ServerNodeId: Set ServerNodeId = CreateObject("OpcLabs.EasyOpc.UA.AddressSpace.UANodeId")
ServerNodeId.StandardName = "Server"
On Error Resume Next
Dim NodeElementCollection: Set NodeElementCollection = Client.BrowseDataVariables(endpointDescriptor, ServerNodeId.ExpandedText)
If Err.Number <> 0 Then
    WScript.Echo "*** Failure: " & Err.Source & ": " & Err.Description
    WScript.Quit
End If
On Error Goto 0

' Display results
Dim NodeElement: For Each NodeElement In NodeElementCollection
    WScript.Echo 
    WScript.Echo "nodeElement.NodeId: " & NodeElement.NodeId
    WScript.Echo "nodeElement.NodeId.ExpandedText: " & NodeElement.NodeId.ExpandedText
    WScript.Echo "nodeElement.DisplayName: " & NodeElement.DisplayName
Next

' Example output:
'
'nodeElement.NodeId: Server_ServerStatus
'nodeElement.NodeId.ExpandedText: nsu=http://opcfoundation.org/UA/ ;i=2256
'nodeElement.DisplayName: ServerStatus

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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