OPC Studio User's Guide and Reference
GetWritableDirectoryContents(IEasyUAFileTransfer,UAEndpointDescriptor,UANodeDescriptor,String) Method



OpcLabs.EasyOpcUA Assembly > OpcLabs.EasyOpc.UA.FileTransfer Namespace > IEasyUAFileTransferExtension Class > GetWritableDirectoryContents Method : GetWritableDirectoryContents(IEasyUAFileTransfer,UAEndpointDescriptor,UANodeDescriptor,String) Method
The OPC UA file transfer object that will perform the operation.
Endpoint descriptor. Identifies the OPC-UA server.
Descriptor of the base node.
Relative path that identifies the directory.
Gets a writable directory contents object for the specified OPC UA directory.
Syntax
'Declaration
 
<ExtensionAttribute()>
<NotNullAttribute()>
Public Overloads Shared Function GetWritableDirectoryContents( _
   ByVal fileTransfer As IEasyUAFileTransfer, _
   ByVal endpointDescriptor As UAEndpointDescriptor, _
   ByVal baseNodeDescriptor As UANodeDescriptor, _
   ByVal subpath As String _
) As IWritableDirectoryContents
'Usage
 
Dim fileTransfer As IEasyUAFileTransfer
Dim endpointDescriptor As UAEndpointDescriptor
Dim baseNodeDescriptor As UANodeDescriptor
Dim subpath As String
Dim value As IWritableDirectoryContents
 
value = IEasyUAFileTransferExtension.GetWritableDirectoryContents(fileTransfer, endpointDescriptor, baseNodeDescriptor, subpath)

Parameters

fileTransfer
The OPC UA file transfer object that will perform the operation.
endpointDescriptor
Endpoint descriptor. Identifies the OPC-UA server.
baseNodeDescriptor
Descriptor of the base node.
subpath
Relative path that identifies the directory.

Return Value

Returns a OpcLabs.BaseLib.Extensions.FileProviders.IWritableDirectoryContents object for the specified OPC UA directory.
Exceptions
ExceptionDescription

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.

If the directory does not exist, an exception is not thrown until the first time a property is accessed or a method is called on the returned object.

The returned writable directory content object allows operations that modify the directory or the file system. If you do not perform such operations and only need read-only operations, such as test for its existence, and enumeration of child files and directories, it is recommended that obtain the OpcLabs.BaseLib.Extensions.FileProviders.IDirectoryContents2 interface instead, by calling the GetDirectoryContents2(IEasyUAFileTransfer,UAEndpointDescriptor,UANodeDescriptor,String) method. This way, you will be protected against calling a method that makes some modifications accidentally.

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.

Requirements

Target Platforms: .NET Framework: Windows 10 (selected versions), Windows 11 (selected versions), Windows Server 2016, Windows Server 2022; .NET: Linux, macOS, Microsoft Windows

See Also