BrowseBranches(IEasyDAClient,String,String,String) Method

Browses the specified branch (or root) in OPC server's address space, and returns information about child branches found. Browse for child branches. Specify machine name, and server class.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<ExtensionAttribute()>
<ElementsNotNullAttribute()>
<NotNullAttribute()>
Public Overloads Shared Function BrowseBranches( _
   ByVal client As IEasyDAClient, _
   ByVal machineName As String, _
   ByVal serverClass As String, _
   ByVal parentItemId As String _
) As DANodeElementCollection

'Usage
 
Dim client As IEasyDAClient
Dim machineName As String
Dim serverClass As String
Dim parentItemId As String
Dim value As DANodeElementCollection
 
value = IEasyDAClientExtension.BrowseBranches(client, machineName, serverClass, parentItemId)

[Extension()]
[ElementsNotNull()]
[NotNull()]
public static DANodeElementCollection BrowseBranches( 
   IEasyDAClient client,
   string machineName,
   string serverClass,
   string parentItemId
)

[Extension()]
[ElementsNotNull()]
[NotNull()]
public:
static DANodeElementCollection^ BrowseBranches( 
   IEasyDAClient^ client,
   String^ machineName,
   String^ serverClass,
   String^ parentItemId
)

Parameters

client: The client object that will perform the operation.
machineName: Name of the machine (empty string for local computer).
serverClass: Contains ProgID of the OPC server to browse.
parentItemId: ID of the parent branch to be browsed (empty string for root)

Return Value

The method returns a keyed collection of OpcLabs.EasyOpc.DataAccess.AddressSpace.DANodeElement values, each containing information about a particular branch found. The keys of the keyed collection are the names of the branches.

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.OperationModel.OpcException	The OPC "Classic" (or OPC XML-DA) 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.OperationModel.OpcException

The OPC "Classic" (or OPC XML-DA) 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 all branches at the root of the address space. For each branch, it displays whether 
// it may have child nodes.

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

namespace DocExamples.DataAccess._EasyDAClient
{
    class BrowseBranches
    {
        public static void Main1()
        {
            // Instantiate the client object.
            var client = new EasyDAClient();
            DANodeElementCollection branchElements;
            try
            {
                branchElements = client.BrowseBranches("", "OPCLabs.KitServer.2", "");
            }
            catch (OpcException opcException)
            {
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message);
                return;
            }

            foreach (DANodeElement branchElement in branchElements)
                Console.WriteLine($"BranchElements(\"{branchElement.Name}\").HasChildren: {branchElement.HasChildren}");
        }


        // Example output:
        //
        //BranchElements("$ServerControl").HasChildren: True
        //BranchElements("Boilers").HasChildren: True
        //BranchElements("Simulation").HasChildren: True
        //BranchElements("SimulateEvents").HasChildren: True
        //BranchElements("Trends").HasChildren: True
        //BranchElements("Demo").HasChildren: True
        //BranchElements("Greenhouse").HasChildren: True
    }
}

# This example shows how to obtain all branches at the root of the address space. For each branch, it displays whether
# it may have child nodes.

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

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


# Instantiate the client object.
client = EasyDAClient()

# Perform the operation.
try:
    nodeElements = IEasyDAClientExtension.BrowseBranches(client, '', 'OPCLabs.KitServer.2', '')
except OpcException as opcException:
    print('*** Failure: ' + opcException.GetBaseException().Message)
    exit()

# Display results.
for nodeElement in nodeElements:
    print('NodeElements["', nodeElement.Name, '"].HasChildren: ', nodeElement.HasChildren, sep='')

VBScript

Rem This example shows how to obtain all branches at the root of the address space. For each branch, it displays whether 
Rem it may have child nodes.

Option Explicit

Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient")
On Error Resume Next
Dim BranchElements: Set BranchElements = Client.BrowseBranches("", "OPCLabs.KitServer.2", "")
If Err.Number <> 0 Then
    WScript.Echo "*** Failure: " & Err.Source & ": " & Err.Description
    WScript.Quit
End If
On Error Goto 0

Dim BranchElement: For Each BranchElement In BranchElements
    WScript.Echo "BranchElements(""" & BranchElement.Name & """).HasChildren: " & BranchElement.HasChildren
Next

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

IEasyDAClientExtension Class
IEasyDAClientExtension Members
Overload List

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