BrowseDataNodes(IEasyUAClient,UAEndpointDescriptor,UANodeDescriptor) Method

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

Syntax

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

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

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

Parameters

client: The client object that will perform the operation.
endpointDescriptor: Endpoint descriptor. Identifies the OPC-UA server.
nodeDescriptor: Node Id.

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.

Remarks

Data nodes are Objects and Variables (Variables are Data Variables and Properties).

Example

// This example shows how to obtain "data nodes" under the "Objects" node, recursively.

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

namespace UADocExamples._EasyUAClient
{
    partial class BrowseDataNodes
    {
        public static void Recursive()
        {
            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();

            try
            {
                BrowseFromNode(client, endpointDescriptor, UAObjectIds.ObjectsFolder, level:0);
            }
            catch (UAException uaException)
            {
                Console.WriteLine($"*** Failure: {uaException.GetBaseException().Message}");
            }
        }

        private static void BrowseFromNode(
            EasyUAClient client,
            UAEndpointDescriptor endpointDescriptor,
            UANodeDescriptor parentNodeDescriptor,
            int level)
        {
            Debug.Assert(!(client is null));
            Debug.Assert(!(endpointDescriptor is null));
            Debug.Assert(!(parentNodeDescriptor is null));

            // Obtain all node elements under parentNodeDescriptor
            UANodeElementCollection nodeElementCollection = 
                client.BrowseDataNodes(endpointDescriptor, parentNodeDescriptor);
            // Remark: BrowseDataNodes(...) may throw UAException; we handle it in the calling method.

            foreach (UANodeElement nodeElement in nodeElementCollection)
            {
                Debug.Assert(!(nodeElement is null));

                Console.Write(new string(' ', level*2));    // indent
                Console.WriteLine(nodeElement);

                // Browse recursively into the node.
                // The UANodeElement has an implicit conversion to UANodeDescriptor.
                BrowseFromNode(client, endpointDescriptor, nodeElement, level + 1);

                // Note that the number of nodes you obtain through recursive browsing may be very large, or even infinite.
                // Production code should contain appropriate safeguards for these cases.
            }
        }


        // Example output:
        //
        //ServerStatus -> nsu=http://opcfoundation.org/UA/ ;i=2256 (Variable) 
        //  StartTime -> nsu=http://opcfoundation.org/UA/ ;i=2257 (Variable) 
        //  CurrentTime -> nsu=http://opcfoundation.org/UA/ ;i=2258 (Variable) 
        //  State -> nsu=http://opcfoundation.org/UA/ ;i=2259 (Variable) 
        //  BuildInfo -> nsu=http://opcfoundation.org/UA/ ;i=2260 (Variable) 
        //    ProductUri -> nsu=http://opcfoundation.org/UA/ ;i=2262 (Variable) 
        //    ManufacturerName -> nsu=http://opcfoundation.org/UA/ ;i=2263 (Variable) 
        //    ProductName -> nsu=http://opcfoundation.org/UA/ ;i=2261 (Variable) 
        //    SoftwareVersion -> nsu=http://opcfoundation.org/UA/ ;i=2264 (Variable) 
        //    BuildNumber -> nsu=http://opcfoundation.org/UA/ ;i=2265 (Variable) 
        //    BuildDate -> nsu=http://opcfoundation.org/UA/ ;i=2266 (Variable) 
        //  SecondsTillShutdown -> nsu=http://opcfoundation.org/UA/ ;i=2992 (Variable) 
        //  ShutdownReason -> nsu=http://opcfoundation.org/UA/ ;i=2993 (Variable) 
        //ServerCapabilities -> nsu=http://opcfoundation.org/UA/ ;i=2268 (Object) 
        //  OperationLimits -> nsu=http://opcfoundation.org/UA/ ;i=11704 (Object) 
        //    MaxNodesPerRead -> nsu=http://opcfoundation.org/UA/ ;i=11705 (Variable) 
        //    MaxNodesPerHistoryReadData -> nsu=http://opcfoundation.org/UA/ ;i=12165 (Variable) 
        //    MaxNodesPerHistoryReadEvents -> nsu=http://opcfoundation.org/UA/ ;i=12166 (Variable) 
        //    MaxNodesPerWrite -> nsu=http://opcfoundation.org/UA/ ;i=11707 (Variable) 
        //    MaxNodesPerHistoryUpdateData -> nsu=http://opcfoundation.org/UA/ ;i=12167 (Variable) 
        //...
    }
}

# This example shows how to obtain "data nodes" under the "Objects" node, recursively.

# 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 *


def browseFromNode(client, endpointDescriptor, parentNodeDescriptor, level):
    assert client is not None
    assert endpointDescriptor is not None
    assert parentNodeDescriptor is not None

    # Obtain all node elements under parentNodeDescriptor
    nodeElementCollection = IEasyUAClientExtension.BrowseDataNodes(client, endpointDescriptor, parentNodeDescriptor)
    # Remark: BrowseDataNodes(...) may throw UAException; we handle it in the calling method.
    #
    for nodeElement in nodeElementCollection:
        assert nodeElement is not None

        print(' '*(level*2), end='')    # indent
        print(nodeElement)

        # Browse recursively into the node.
        # The UANodeElement has an implicit conversion to UANodeDescriptor.
        browseFromNode(client, endpointDescriptor, nodeElement.ToUANodeDescriptor(), level + 1)

        # Note that the number of nodes you obtain through recursive browsing may be very large, or even infinite.
        # Production code should contain appropriate safeguards for these cases.


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()

try:
    browseFromNode(client, endpointDescriptor, UANodeDescriptor(UAObjectIds.ObjectsFolder), 0)
except UAException as uaException:
    print('*** Failure: ' + uaException.GetBaseException().Message)
    exit()

print()
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

Reference

IEasyUAClientExtension Class
IEasyUAClientExtension Members
Overload List

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