Delete Method (IWritableFileInfo)

Permanently deletes a file.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
Sub Delete()

'Usage
 
Dim instance As IWritableFileInfo
 
instance.Delete()

void Delete()

void Delete();

Exceptions

Exception	Description
System.ArgumentException	One of the arguments provided to a method is not valid. 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.
System.IO.IOException	An I/O error has occurred. 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.NotSupportedException	An invoked method is not supported at all, or is not supported with the parameters used to create the object.
System.Security.SecurityException	A security error was detected. 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.UnauthorizedAccessException	The operating system has denied access because of an I/O error or a specific type of security error. 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

This method is similar in purpose to System.IO.FileInfo.Delete, but is generalized for any kind of writable file info, not just files in the physical file system.

If the file does not exist, this method does nothing. If you want an exception be thrown when the file does not exist, use the IWritableFileInfoExtension.DeleteExisting extension method.

Example

// Shows how to create and delete OPC UA files, using the file provider model.

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

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

            // A node that represents an OPC UA file system (a root directory).
            UANodeDescriptor fileSystemNodeDescriptor = "nsu=http://www.unifiedautomation.com/DemoServer/ ;s=Demo.Files.FileSystem";

            // 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();

            Console.WriteLine("Getting writable file provider...");
            IWritableFileProvider writableFileProvider =
                fileTransferClient.GetWritableFileProvider(endpointDescriptor, fileSystemNodeDescriptor);
            // 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.

            // Create two files, and delete the first one.
            try
            {
                string fileName1 = "MyFile1-" + random.Next();
                Console.WriteLine($"Creating first file, '{fileName1}'...");
                IWritableFileInfo writableFileInfo1 = writableFileProvider.GetWritableFileInfo(fileName1);
                writableFileInfo1.WriteAllBytes(Array.Empty<byte>());

                string fileName2 = "MyFile2-" + random.Next();
                Console.WriteLine($"Creating second file, '{fileName2}'...");
                IWritableFileInfo writableFileInfo2 = writableFileProvider.GetWritableFileInfo(fileName2);
                writableFileInfo2.WriteAllBytes(Array.Empty<byte>());

                Console.WriteLine("Deleting the first file...");
                writableFileInfo1.Delete();
            }
            // Methods in the file provider model throw IOException and other exceptions, but not UAException.
            catch (Exception exception)
            {
                Console.WriteLine($"*** Failure: {exception.GetBaseException().Message}");
                return;
            }

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

# Shows how to create and delete OPC UA files, using the file provider model.

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

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


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

# A node that represents an OPC UA file system (a root directory).
fileSystemNodeDescriptor = UANodeDescriptor('nsu=http://www.unifiedautomation.com/DemoServer/ ;s=Demo.Files.FileSystem')

# 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)

print('Getting writable file provider...')
writableFileProvider = IEasyUAFileTransferExtension.GetWritableFileProvider(fileTransferClient,
                                                                            endpointDescriptor,
                                                                            fileSystemNodeDescriptor)
# 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.

# Create two files, and delete the first one.
try:
    fileName1 = 'MyFile1-' + str(random.randint(0, 999_999_999))
    print("Creating first file, '", fileName1, "'...", sep='')
    writableFileInfo1 = writableFileProvider.GetWritableFileInfo(fileName1)
    IWritableFileInfoExtension.WriteAllBytes(writableFileInfo1, Array.Empty[Byte]())

    fileName2 = 'MyFile2-' + str(random.randint(0, 999_999_999))
    print("Creating second file, '", fileName2, "'...", sep='')
    writableFileInfo2 = writableFileProvider.GetWritableFileInfo(fileName2)
    IWritableFileInfoExtension.WriteAllBytes(writableFileInfo2, Array.Empty[Byte]())

    print('Deleting the first file...')
    writableFileInfo1.Delete()

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

print()
print('Finished.')

' Shows how to create and delete OPC UA files, using the file provider model.

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

Namespace FileProviders._WritableFileInfo

    Friend Class CreateAndDelete

        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")

            ' A node that represents an OPC UA file system (a root directory).
            Dim fileSystemNodeDescriptor As UANodeDescriptor =
                "nsu=http://www.unifiedautomation.com/DemoServer/ ;s=Demo.Files.FileSystem"

            ' 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

            Console.WriteLine("Getting writable file provider...")
            Dim writableFileProvider As IWritableFileProvider =
                fileTransferClient.GetWritableFileProvider(endpointDescriptor, fileSystemNodeDescriptor)
            ' 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.

            ' Create two files, and delete the first one.
            Try
                Dim fileName1 As String = "MyFile1-" & random.Next()
                Console.WriteLine($"Creating first file, '{fileName1}'...")
                Dim writableFileInfo1 As IWritableFileInfo = writableFileProvider.GetWritableFileInfo(fileName1)
                writableFileInfo1.WriteAllBytes(Array.Empty(Of Byte))

                Dim fileName2 As String = "MyFile2-" & random.Next()
                Console.WriteLine($"Creating second file, '{fileName2}'...")
                Dim writableFileInfo2 As IWritableFileInfo = writableFileProvider.GetWritableFileInfo(fileName2)
                writableFileInfo2.WriteAllBytes(Array.Empty(Of Byte))

                Console.WriteLine("Deleting the first file...")
                writableFileInfo1.Delete()

                ' 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

            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

IWritableFileInfo Interface
IWritableFileInfo Members
DeleteExisting Method

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