GetFileInfo2(IEasyUAFileTransfer,UAEndpointDescriptor,UANodeDescriptor,IReadOnlyList<String>,String) Method

Gets a file info object for the specified OPC UA file.

Syntax

[Extension()]
[NotNull()]
public static IFileInfo2 GetFileInfo2( 
   IEasyUAFileTransfer fileTransfer,
   UAEndpointDescriptor endpointDescriptor,
   UANodeDescriptor baseNodeDescriptor,
   IReadOnlyList<string> basePathElements,
   string subpath
)

[Extension()]
[NotNull()]
public:
static IFileInfo2^ GetFileInfo2( 
   IEasyUAFileTransfer^ fileTransfer,
   UAEndpointDescriptor^ endpointDescriptor,
   UANodeDescriptor^ baseNodeDescriptor,
   IReadOnlyList<String^>^ basePathElements,
   String^ subpath
)

'Declaration
 
<ExtensionAttribute()>
<NotNullAttribute()>
Public Overloads Shared Function GetFileInfo2( _
   ByVal fileTransfer As IEasyUAFileTransfer, _
   ByVal endpointDescriptor As UAEndpointDescriptor, _
   ByVal baseNodeDescriptor As UANodeDescriptor, _
   ByVal basePathElements As IReadOnlyList(Of String), _
   ByVal subpath As String _
) As IFileInfo2

'Usage
 
Dim fileTransfer As IEasyUAFileTransfer
Dim endpointDescriptor As UAEndpointDescriptor
Dim baseNodeDescriptor As UANodeDescriptor
Dim basePathElements As IReadOnlyList(Of String)
Dim subpath As String
Dim value As IFileInfo2
 
value = IEasyUAFileTransferExtension.GetFileInfo2(fileTransfer, endpointDescriptor, baseNodeDescriptor, basePathElements, subpath)

Parameters

fileTransfer

The OPC UA file transfer object that will perform the operation.

This is typically the EasyUAFileTransferClient object.

The value of this parameter cannot be null (Nothing in Visual Basic).

endpointDescriptor

Endpoint descriptor. Identifies the OPC-UA server.

Because the OpcLabs.EasyOpc.UA.UAEndpointDescriptor has implicit conversions from System.String and System.Uri, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a string (representing the endpoint URL, or a so-called OPC UA endpoint descriptor string), or a System.Uri object, in place of this parameter, and the corresponding endpoint descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the OpcLabs.EasyOpc.UA.UAEndpointDescriptor.FromString or OpcLabs.EasyOpc.UA.UAEndpointDescriptor.FromUri static method instead.

Also, because the OpcLabs.EasyOpc.UA.Discovery.UAApplicationElement and OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement have an implicit conversion to OpcLabs.EasyOpc.UA.UAEndpointDescriptor, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a OpcLabs.EasyOpc.UA.Discovery.UAApplicationElement or OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement (results from OPC UA discovery) in place of this parameter, and the corresponding endpoint descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can convert a (non-null) OpcLabs.EasyOpc.UA.Discovery.UAApplicationElement or OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement to OpcLabs.EasyOpc.UA.UAEndpointDescriptor using the ToUAEndpointDescriptor or ToUAEndpointDescriptor method instead.

If you are using OPC Wizard (for server development), an implicit conversion from OpcLabs.EasyOpc.UA.EasyUAServerCore can be used in the same way to simply pass the server object in place of this parameter, which will use its OpcLabs.EasyOpc.UA.EasyUAServerCore.EffectiveServerDescriptor property for the connection.

The value of this parameter cannot be null (Nothing in Visual Basic).

baseNodeDescriptor

Descriptor of the base node of the named node path.

Because the OpcLabs.EasyOpc.UA.UANodeDescriptor has implicit conversions from OpcLabs.EasyOpc.UA.AddressSpace.UANodeId, OpcLabs.EasyOpc.UA.AddressSpace.UANodeElement, OpcLabs.EasyOpc.UA.Navigation.UABrowsePath and System.String, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a OpcLabs.EasyOpc.UA.AddressSpace.UANodeId object (representing the Id of the OPC UA node), a node element object (from OPC UA browsing), OpcLabs.EasyOpc.UA.Navigation.UABrowsePath object (representing OPC UA absolute browse path), or a string (with expanded node Id text) in place of this parameter, and the corresponding node descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the OpcLabs.EasyOpc.UA.UANodeDescriptor.FromString, OpcLabs.EasyOpc.UA.UANodeDescriptor.FromUABrowsePath, OpcLabs.EasyOpc.UA.UANodeDescriptor.FromUANodeElement or OpcLabs.EasyOpc.UA.UANodeDescriptor.FromUANodeId static method instead.

If you are using OPC Wizard (for server development), an implicit conversion from OpcLabs.EasyOpc.UA.NodeSpace.UAServerNode can be used in the same way to simply pass the server node in place of this parameter, which will use its OpcLabs.EasyOpc.UA.NodeSpace.UAServerNode.EffectiveNodeDescriptor property for the operation.

The value of this parameter cannot be null (Nothing in Visual Basic).

basePathElements

The path elements of the named node path, i.e. the names of nodes from the base node forwards.

The value of this parameter cannot be null (Nothing in Visual Basic).

The individual elements of the parameter value cannot be null (Nothing in Visual Basic).

subpath

Relative path that identifies the file.

The value of this parameter can be null (Nothing in Visual Basic).

Return Value

Returns a Microsoft.Extensions.FileProviders.IFileInfo object for the specified OPC UA file.

This method never returns null (Nothing in Visual Basic).

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.

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.

Remarks

This method does not make any OPC UA operation, and does not throw the usual OpcLabs.EasyOpc.UA.OperationModel.UAException. You can therefore always safely use it to obtain the result interface. All OPC UA operations are made later, on the returned object, and also operation-related exceptions are thrown at that time.

An exception is not thrown if the file does not exist; rather, it will be thrown the first time the object's properties are accessed or its methods are called.

The returned file info object allows only read-only operations on the file - such as test for its existence, and opening it for read access. If you need operations that modify the file data or the file system, you need to obtain the OpcLabs.BaseLib.Extensions.FileProviders.IWritableFileInfo interface instead, by calling the GetWritableFileInfo(IEasyUAFileTransfer,UAEndpointDescriptor,UANamedNodeDescriptor) method.

The file metadata in the file info object is a snapshot taken at the time ihe metadata was first accessed. It does not reflect further changes to the metadata, even if you read it repeatedly later.

Accessing OPC UA files and directories over the abstract file provider model (based on Microsoft.Extensions.FileProviders.IFileProvider, Microsoft.Extensions.FileProviders.IFileInfo, OpcLabs.BaseLib.Extensions.FileProviders.IDirectoryContents2 and their "writable" counterparts), which is what this method does, is highly recommended over the other, lower-level methods. Once you obtained the generalized interface in the file provider model, operations on files and directories can be performed using just names and paths, without having to deal with OPC UA nodes and references.

This is an extension method (info: C#, VB.NET). In languages that have support for extensions methods (such as C# and VB.NET), you can use the extension method as if it were a regular method on the object that is its first parameter. In other languages (such as with Python.NET), you will call the extension as a static method, and pass it the object on which it acts as its first parameter.

Example

// Shows how to read the full contents of an OPC UA file at once, using the file provider model.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-CSharp .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

using System;
using System.Text;
using OpcLabs.BaseLib.Extensions.FileProviders;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.FileTransfer;

namespace UADocExamples.FileProviders._FileInfo2
{
    class ReadAllBytes
    {
        public static void Main1()
        {
            // Unified Automation .NET based demo server (UaNETServer/UaServerNET.exe)
            UAEndpointDescriptor endpointDescriptor = "opc.tcp://localhost:48030";

            // A node that represents an instance of OPC UA FileType object.
            UANodeDescriptor fileNodeDescriptor = "nsu=http://www.unifiedautomation.com/DemoServer/ ;s=Demo.Files.TextFile";
            
            // Instantiate the file transfer client object
            var fileTransferClient = new EasyUAFileTransferClient();

            Console.WriteLine("Getting file info...");
            IFileInfo2 fileInfo2 = fileTransferClient.GetFileInfo2(endpointDescriptor, fileNodeDescriptor);
            // From this point onwards, the code is independent of the concrete realization of the file provider, and would
            // be identical e.g. for files in the physical file system, if the corresponding file provider was used.

            // Read in all contents from a specified file node.
            byte[] bytes;
            try
            {
                Console.WriteLine("Reading the whole file...");
                bytes = fileInfo2.ReadAllBytes();
            }
            // Methods in the file provider model throw IOException and other exceptions, but not UAException.
            catch (Exception exception)
            {
                Console.WriteLine($"*** Failure: {exception.GetBaseException().Message}");
                return;
            }

            // Display result
            Console.WriteLine();
            // We know that the file contains text, so we convert the received data to a string. If the file contents was
            // binary, you would process the data according to their format.
            string text = Encoding.UTF8.GetString(bytes);
            Console.WriteLine("File content:");
            Console.WriteLine(text);

            Console.WriteLine();
            Console.WriteLine("Finished...");
        }
    }
}

' Shows how to read the full contents of an OPC UA file at once, using the file provider model.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET .
' Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
' a commercial license in order to use Online Forums, and we reply to every post.

Imports System.Text
Imports OpcLabs.BaseLib.Extensions.FileProviders
Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.FileTransfer

Namespace FileProviders._FileInfo2

    Friend Class ReadAllBytes

        Public Shared Sub Main1()

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

            ' A node that represents an instance of OPC UA FileType object.
            Dim fileNodeDescriptor As UANodeDescriptor =
                "nsu=http://www.unifiedautomation.com/DemoServer/ ;s=Demo.Files.TextFile"

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

            Console.WriteLine("Getting file info...")
            Dim fileInfo2 As IFileInfo2 =
                fileTransferClient.GetFileInfo2(endpointDescriptor, fileNodeDescriptor)
            ' From this point onwards, the code is independent of the concrete realization of the file provider, and would
            ' be identical e.g. for files in the physical file system, if the corresponding file provider was used.

            ' Read in all contents from a specified file node.
            Dim bytes As Byte()
            Try
                Console.WriteLine("Reading the whole file...")
                bytes = fileInfo2.ReadAllBytes()

                ' Methods in the file provider model throw IOException and other exceptions, but not UAException.
            Catch exception As Exception
                Console.WriteLine("*** Failure: {0}", exception.GetBaseException.Message)
                Exit Sub
            End Try

            ' Display result
            Console.WriteLine()
            ' We know that the file contains text, so we convert the received data to a string. If the file contents was
            ' binary, you would process the data according to their format.
            Dim text As String = Encoding.UTF8.GetString(bytes)
            Console.WriteLine("File content:")
            Console.WriteLine(text)

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

# Shows how to read the full contents of an OPC UA file at once, using the file provider model.
#
# 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 .
# Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
# a commercial license in order to use Online Forums, and we reply to every post.
# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc

# Import .NET namespaces.
from System.Text import *
from OpcLabs.BaseLib.Extensions.FileProviders import *
from OpcLabs.EasyOpc.UA import *
from OpcLabs.EasyOpc.UA.FileTransfer import *
from OpcLabs.EasyOpc.UA.Navigation import *


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

# A node that represents an instance of OPC UA FileType object.
fileNodeDescriptor = UANodeDescriptor('nsu=http://www.unifiedautomation.com/DemoServer/ ;s=Demo.Files.TextFile')

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

print('Getting file info......')
fileInfo2 = IEasyUAFileTransferExtension.GetFileInfo2(fileTransferClient,
                                                      endpointDescriptor,
                                                      UANamedNodeDescriptor(fileNodeDescriptor))
# From this point onwards, the code is independent of the concrete realization of the file provider, and would
# be identical e.g. for files in the physical file system, if the corresponding file provider was used.

# Read in all contents from a specified file node.
try:
    print('Reading the whole file...')
    bytes = IFileInfoExtension.ReadAllBytes(fileInfo2)

# Methods in the file provider model throw IOException and other exceptions, but not UAException.
except Exception as exception:
    print('*** Failure: ' + exception.GetBaseException().Message)
    exit()

# Display result.
print()
# We know that the file contains text, so we convert the received data to a string. If the file contents was
# binary, you would process the data according to their format.
text = Encoding.UTF8.GetString(bytes)
print('File content:')
print(text)


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

IEasyUAFileTransferExtension Class
IEasyUAFileTransferExtension Members
Overload List
GetDirectoryContents2(IEasyUAFileTransfer,UAEndpointDescriptor,UANamedNodePath) Method
GetWritableFileInfo(IEasyUAFileTransfer,UAEndpointDescriptor,UANamedNodeDescriptor) Method

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