BrowseFiles(IEasyUAFileTransfer,UAEndpointDescriptor,UANodeDescriptor) Method

Browses for files under the specified OPC UA directory.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<ExtensionAttribute()>
<ElementsNotNullAttribute()>
<NotNullAttribute()>
Public Overloads Shared Function BrowseFiles( _
   ByVal fileTransfer As IEasyUAFileTransfer, _
   ByVal endpointDescriptor As UAEndpointDescriptor, _
   ByVal directoryNodeDescriptor As UANodeDescriptor _
) As Dictionary(Of String,UANodeDescriptor)

'Usage
 
Dim fileTransfer As IEasyUAFileTransfer
Dim endpointDescriptor As UAEndpointDescriptor
Dim directoryNodeDescriptor As UANodeDescriptor
Dim value As Dictionary(Of String,UANodeDescriptor)
 
value = IEasyUAFileTransferExtension.BrowseFiles(fileTransfer, endpointDescriptor, directoryNodeDescriptor)

[Extension()]
[ElementsNotNull()]
[NotNull()]
public static Dictionary<string,UANodeDescriptor> BrowseFiles( 
   IEasyUAFileTransfer fileTransfer,
   UAEndpointDescriptor endpointDescriptor,
   UANodeDescriptor directoryNodeDescriptor
)

[Extension()]
[ElementsNotNull()]
[NotNull()]
public:
static Dictionary<String^,UANodeDescriptor^>^ BrowseFiles( 
   IEasyUAFileTransfer^ fileTransfer,
   UAEndpointDescriptor^ endpointDescriptor,
   UANodeDescriptor^ directoryNodeDescriptor
)

Parameters

fileTransfer: The OPC UA file transfer object that will perform the operation.
endpointDescriptor: Endpoint descriptor. Identifies the OPC-UA server.
directoryNodeDescriptor: Node descriptor of the OPC UA directory.

Return Value

Returns a dictionary of node descriptors of the files under the specified OPC UA directory.

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

The directoryNodeDescriptor must be an existing node in the server, of object type OpcLabs.EasyOpc.UA.AddressSpace.Standard.UAObjectTypeIds.FileDirectoryType.

If you need the file names, use the ListFileNames(IEasyUAFileTransfer,UAEndpointDescriptor,UANamedNodePath)method.

Recommendation: Whenever possible, do not use this method directly, and use a higher-level abstraction instead. See e.g. the GetDirectoryContents2(IEasyUAFileTransfer,UAEndpointDescriptor,UANamedNodePath) method, which allows you to obtain an object that can be enumerated for files and directories underneath, in a way that is generic and not tied to OPC UA specifics.

Example

// Shows how to browse for OPC UA files, using the file transfer client.
// Note: Consider using a higher-level abstraction, OPC UA file provider, instead.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

using System;
using System.Collections.Generic;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.Extensions;
using OpcLabs.EasyOpc.UA.FileTransfer;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples.FileTransfer._EasyUAFileTransferClient
{
    class BrowseFiles
    {
        public static void Main1()
        {
            // Unified Automation .NET based demo server (UaNETServer/UaServerNET.exe)
            var endpointDescriptor = new UAEndpointDescriptor("opc.tcp://localhost:48030")
                .WithUserNameIdentity("john", "master");

            // An object that aggregates an OPC UA file system.
            UANodeDescriptor objectDescriptor = "nsu=http://www.unifiedautomation.com/DemoServer/ ;s=Demo.Files";

            // Create a random number generator - will be used for file/directory names.
            var random = new Random();
            
            // Instantiate the file transfer client object
            var fileTransferClient = new EasyUAFileTransferClient();

            // Create two files, and then browse the directory that contains them.
            Dictionary<string, UANodeDescriptor> fileNodeDescriptorDictionary;
            try
            {
                // The file system node is a root directory of the file system.
                Console.WriteLine("Getting file system...");
                UANodeDescriptor fileSystemNodeDescriptor = fileTransferClient.GetFileSystem(endpointDescriptor, objectDescriptor);

                string fileName1 = "MyFile1-" + random.Next();
                Console.WriteLine($"Creating first file, '{fileName1}'...");
                fileTransferClient.CreateFile(endpointDescriptor, fileSystemNodeDescriptor, fileName1);

                string fileName2 = "MyFile2-" + random.Next();
                Console.WriteLine($"Creating second file, '{fileName2}'...");
                fileTransferClient.CreateFile(endpointDescriptor, fileSystemNodeDescriptor, fileName2);

                Console.WriteLine("Browsing for files...");
                fileNodeDescriptorDictionary = fileTransferClient.BrowseFiles(endpointDescriptor, fileSystemNodeDescriptor);
                // If you want browse for directories, use the BrowseDirectories method instead.
            }
            catch (UAException uaException)
            {
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message);
                return;
            }

            // Display result
            Console.WriteLine();
            foreach (KeyValuePair<string, UANodeDescriptor> pair in fileNodeDescriptorDictionary)
                Console.WriteLine(pair);
            
            Console.WriteLine();
            Console.WriteLine("Finished...");
        }
    }
}

# Shows how to browse for OPC UA files, using the file transfer client.
# Note: Consider using a higher-level abstraction, OPC UA file provider, instead.
#
# 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 random

# Import .NET namespaces.
from OpcLabs.EasyOpc.UA import *
from OpcLabs.EasyOpc.UA.Extensions import *
from OpcLabs.EasyOpc.UA.FileTransfer import *
from OpcLabs.EasyOpc.UA.OperationModel import *


# Unified Automation .NET based demo server (UaNETServer/UaServerNET.exe).
endpointDescriptor = UAEndpointDescriptor('opc.tcp://localhost:48030')
endpointDescriptor = UAEndpointDescriptorExtension.WithUserNameIdentity(endpointDescriptor,'john', 'master')

# An object that aggregates an OPC UA file system.
objectDescriptor = UANodeDescriptor('nsu=http://www.unifiedautomation.com/DemoServer/ ;s=Demo.Files')

# Create a random number generator - will be used for file/directory names.
random = random.Random()

# Instantiate the file transfer client object.
fileTransferClient = EasyUAFileTransferClient()

# Prevent prompt to trust the server certificate (INSECURE, used just for smooth example flow).
EasyUAClient.SharedParameters.EngineParameters.CertificateAcceptancePolicy.TrustEndpointUrlString(
    endpointDescriptor.UrlString)

# Create two files, and then browse the directory that contains them.
try:
    # The file system node is a root directory of the file system.
    print('Getting file system...')
    fileSystemNodeDescriptor = IEasyUAFileTransferExtension.GetFileSystem(fileTransferClient,
                                                                          endpointDescriptor, objectDescriptor)

    fileName1 = 'MyFile1-' + str(random.randint(0, 999_999_999))
    print("Creating first file, '", fileName1, "'...", sep='')
    IEasyUAFileTransferExtension.CreateFile(fileTransferClient, endpointDescriptor, fileSystemNodeDescriptor, fileName1)

    fileName2 = 'MyFile2-' + str(random.randint(0, 999_999_999))
    print("Creating second file, '", fileName1, "'...", sep='')
    IEasyUAFileTransferExtension.CreateFile(fileTransferClient, endpointDescriptor, fileSystemNodeDescriptor, fileName2)

    print('Browsing for files...')
    fileNodeDescriptorDictionary = IEasyUAFileTransferExtension.BrowseFiles(fileTransferClient,
                                                                            endpointDescriptor,
                                                                            fileSystemNodeDescriptor)
    # If you want browse for directories, use the BrowseDirectories method instead.

except UAException as uaException:
    print('*** Failure: ' + uaException.GetBaseException().Message)
    exit()

# Display results.
print()
for pair in fileNodeDescriptorDictionary:
    print(pair)

print()
print('Finished.')

' Shows how to copy an OPC UA file, using the file transfer client.
' Note: Consider using a higher-level abstraction, OPC UA file provider, instead.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.Extensions
Imports OpcLabs.EasyOpc.UA.FileTransfer
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace FileTransfer._EasyUAFileTransferClient

    Friend Class BrowseFiles

        Public Shared Sub Main1()

            ' Unified Automation .NET based demo server (UaNETServer/UaServerNET.exe)
            Dim endpointDescriptor As UAEndpointDescriptor =
                New UAEndpointDescriptor("opc.tcp://localhost:48030") _
                .WithUserNameIdentity("john", "master")

            ' An object that aggregates an OPC UA file system.
            Dim objectDescriptor As UANodeDescriptor = "nsu=http://www.unifiedautomation.com/DemoServer/ ;s=Demo.Files"

            ' Create a random number generator - will be used for file/directory names.
            Dim random = New Random

            ' Instantiate the file transfer client object
            Dim fileTransferClient = New EasyUAFileTransferClient

            ' Create two files, and then browse the directory that contains them.
            Dim fileNodeDescriptorDictionary As IReadOnlyDictionary(Of String, UANodeDescriptor)
            Try
                ' The file system node is a root directory of the file system.
                Console.WriteLine("Getting file system...")
                Dim fileSystemNodeDescriptor As UANodeDescriptor = fileTransferClient.GetFileSystem(endpointDescriptor, objectDescriptor)

                Dim fileName1 As String = "MyFile1-" & random.Next()
                Console.WriteLine($"Creating first file, '{fileName1}'...")
                fileTransferClient.CreateFile(endpointDescriptor, fileSystemNodeDescriptor, fileName1)

                Dim fileName2 As String = "MyFile2-" & random.Next()
                Console.WriteLine($"Creating second file, '{fileName2}'...")
                fileTransferClient.CreateFile(endpointDescriptor, fileSystemNodeDescriptor, fileName2)

                Console.WriteLine("Browsing for files...")
                fileNodeDescriptorDictionary = fileTransferClient.BrowseFiles(endpointDescriptor, fileSystemNodeDescriptor)
                ' If you want browse for directories, use the BrowseDirectories method instead.
            Catch uaException As UAException
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException.Message)
                Exit Sub
            End Try

            ' Display result
            Console.WriteLine()
            For Each pair In fileNodeDescriptorDictionary
                Console.WriteLine(pair)
            Next pair

            Console.WriteLine()
            Console.WriteLine("Finished...")
        End Sub
    End Class
End Namespace

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

IEasyUAFileTransferExtension Class
IEasyUAFileTransferExtension Members
Overload List
BrowseDirectories(IEasyUAFileTransfer,UAEndpointDescriptor,UANamedNodePath) Method
EnumerateFiles(IEasyUAFileTransfer,UAEndpointDescriptor,UANamedNodePath) Method
ListFileNames(IEasyUAFileTransfer,UAEndpointDescriptor,UANamedNodePath) Method

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