OPC Studio User's Guide and Reference
Examples - OPC Data Access - Browse nodes recursively and read their values
// Recursively browses and displays the nodes in the OPC address space, and attempts to read and display values of all OPC 
// items it finds.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

using System;
using System.Diagnostics;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.AddressSpace;
using OpcLabs.EasyOpc.OperationModel;

namespace DocExamples.DataAccess._EasyDAClient
{
    partial class BrowseNodes
    {
        const string ServerClass = "OPCLabs.KitServer.2";

        // Instantiate the client object.
        static readonly EasyDAClient Client = new EasyDAClient();

        static void BrowseAndReadFromNode(string parentItemId)
        {
            // Obtain all node elements under parentItemId
            var browseParameters = new DABrowseParameters(); // no filtering whatsoever
            DANodeElementCollection nodeElementCollection = Client.BrowseNodes("", ServerClass, parentItemId,
                browseParameters);
            // Remark: that BrowseNodes(...) may also throw OpcException; a production code should contain handling for it, here 
            // omitted for brevity.

            foreach (DANodeElement nodeElement in nodeElementCollection)
            {
                Debug.Assert(nodeElement != null);

                // If the node is a leaf, it might be possible to read from it
                if (nodeElement.IsLeaf)
                {
                    // Determine what the display - either the value read, or exception message in case of failure.
                    string display;
                    try
                    {
                        object value = Client.ReadItemValue("", ServerClass, nodeElement);
                        display = $"{value}";
                    }
                    catch (OpcException exception)
                    {
                        display = $"** {exception.GetBaseException().Message} **";
                    }

                    Console.WriteLine("{0} -> {1}", nodeElement.ItemId, display);
                }
                // If the node is not a leaf, just display its itemId
                else
                    Console.WriteLine("{0}", nodeElement.ItemId);

                // If the node is a branch, browse recursively into it.
                if (nodeElement.IsBranch &&
                    (nodeElement.ItemId != "SimulateEvents")
                    /* this branch is too big for the purpose of this example */)
                    BrowseAndReadFromNode(nodeElement);
            }
        }

        public static void RecursiveWithRead()
        {
            Console.WriteLine("Browsing and reading values...");
            // Set timeout to only wait 1 second - default would be 1 minute to wait for good quality that may never come.
            Client.InstanceParameters.Timeouts.ReadItem = 1000;

            // Do the actual browsing and reading, starting from root of OPC address space (denoted by empty string for itemId)
            try
            {
                BrowseAndReadFromNode("");
            }
            catch (OpcException opcException)
            {
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message);
            }
        }
    }
}
# Recursively browses and displays the nodes in the OPC address space, and attempts to read and display values of all
# OPC items it finds.
#
# 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 .
# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc

# Import .NET namespaces.
from OpcLabs.EasyOpc import *
from OpcLabs.EasyOpc.DataAccess import *
from OpcLabs.EasyOpc.OperationModel import *

SERVER_CLASS = 'OPCLabs.KitServer.2'


def browseAndReadFromNode(parentItemId):
    global client
    #
    # Obtain all node elements under parentItemId.
    browseParameters = DABrowseParameters()  # no filtering whatsoever
    nodeElementCollection = client.BrowseNodes(ServerDescriptor(SERVER_CLASS),
                                               DANodeDescriptor(parentItemId),
                                               browseParameters)
    # BrowseNodes(...) may also throw OpcException; here it is handled by the caller.
    #
    for nodeElement in nodeElementCollection:
        assert nodeElement is not None
        print(nodeElement)

        # If the node is a leaf, it might be possible to read from it.
        if nodeElement.IsLeaf:
            # Determine what to display - either the value read, or exception message in case of failure.
            try:
                value = IEasyDAClientExtension.ReadItemValue(client, '', SERVER_CLASS, nodeElement.ItemId)
                display = value
            except OpcException as opcException:
                display = '** ' + opcException.GetBaseException().Message + ' **'
            #
            print(nodeElement.ItemId, ' -> ', display, sep='')
        # If the node is not a leaf, just display its itemId.
        else:
            print(nodeElement.ItemId)

        # If the node is a branch, browse recursively into it.
        if nodeElement.IsBranch and nodeElement.ItemId != 'SimulateEvents':
            # this branch is too big for the purpose of this example
            browseAndReadFromNode(nodeElement.ItemId)


# Instantiate the client object.
client = EasyDAClient('Browsing and reading values...')

print('Browsing and reading values...')

# Do the actual browsing and reading, starting from root of OPC address space (denoted by empty string for itemId).
try:
    browseAndReadFromNode('')
except OpcException as opcException:
    print('*** Failure: ' + opcException.GetBaseException().Message)
    exit()

print()
print('Finished.')
' Recursively browses and displays the nodes in the OPC address space, and attempts to read and display values of all OPC 
' items it finds.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.DataAccess.AddressSpace
Imports OpcLabs.EasyOpc.OperationModel

Namespace DataAccess._EasyDAClient
    Partial Friend Class BrowseNodes
        Private Const ServerClass As String = "OPCLabs.KitServer.2"

        Private Shared ReadOnly Client As New EasyDAClient()

        Private Shared Sub BrowseAndReadFromNode(parentItemId As String)
            ' Obtain all node elements under parentItemId
            Dim browseParameters = New DABrowseParameters() ' no filtering whatsoever
            Dim nodeElementCollection As DANodeElementCollection = Client.BrowseNodes("", ServerClass, parentItemId, browseParameters)
            ' Remark: that BrowseNodes(...) may also throw OpcException; a production code should contain handling for it, here 
            ' omitted for brevity.

            For Each nodeElement As DANodeElement In nodeElementCollection
                Debug.Assert(nodeElement IsNot Nothing)

                ' If the node is a leaf, it might be possible to read from it
                If nodeElement.IsLeaf Then
                    ' Determine what the display - either the value read, or exception message in case of failure.
                    Dim display As String
                    Try
                        Dim value As Object = Client.ReadItemValue("", ServerClass, nodeElement.ItemId)
                        display = String.Format("{0}", value)
                    Catch exception As OpcException
                        display = String.Format("** {0} **", exception.GetBaseException().Message)
                    End Try

                    Console.WriteLine("{0} -> {1}", nodeElement.ItemId, display)
                    ' If the node is not a leaf, just display its itemId
                Else
                    Console.WriteLine("{0}", nodeElement.ItemId)
                End If

                ' If the node is a branch, browse recursively into it.
                If nodeElement.IsBranch AndAlso (nodeElement.ItemId <> "SimulateEvents") Then ' this branch is too big for the purpose of this example
                    BrowseAndReadFromNode(nodeElement.ItemId)
                End If
            Next nodeElement
        End Sub

        Shared Sub RecursiveWithRead()
            Console.WriteLine("Browsing and reading values...")
            ' Set timeout to only wait 1 second - default would be 1 minute to wait for good quality that may never come.
            Client.InstanceParameters.Timeouts.ReadItem = 1000

            ' Do the actual browsing and reading, starting from root of OPC address space (denoted by empty string for itemId)
            Try
                BrowseAndReadFromNode("")
            Catch opcException As OpcException
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message)
                Exit Sub
            End Try
        End Sub
    End Class
End Namespace

 

See Also

Conceptual