OPC Studio User's Guide and Reference
GetFileProvider2 Method



OpcLabs.EasyOpcUA Assembly > OpcLabs.EasyOpc.UA.FileTransfer Namespace > IEasyUAFileTransferExtension Class : GetFileProvider2 Method
The OPC UA file transfer object that will perform the operation.
Endpoint descriptor. Identifies the OPC-UA server.
Node descriptor of the OPC UA directory.
Gets a file provider on the specified OPC UA directory.
Syntax
'Declaration
 
<ExtensionAttribute()>
<NotNullAttribute()>
Public Shared Function GetFileProvider2( _
   ByVal fileTransfer As IEasyUAFileTransfer, _
   ByVal endpointDescriptor As UAEndpointDescriptor, _
   ByVal directoryNodeDescriptor As UANodeDescriptor _
) As IFileProvider2
'Usage
 
Dim fileTransfer As IEasyUAFileTransfer
Dim endpointDescriptor As UAEndpointDescriptor
Dim directoryNodeDescriptor As UANodeDescriptor
Dim value As IFileProvider2
 
value = IEasyUAFileTransferExtension.GetFileProvider2(fileTransfer, endpointDescriptor, 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 file provider 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.

A file provider is an abstraction of a file system, with access to its files and directories. Concrete implementations include a file provider for the physical file system (provided by the operating system), file providers for embedded resources, and, as in this case, a file provider for OPC UA File Transfer facility.

The returned file provider object allows only read-only operations on the file system - such as obtaining a read-only file info or directory contents, or setting up change notifications for the changes in the file system. If you need operations that modify the file system or data in its files, you need to obtain the OpcLabs.BaseLib.Extensions.FileProviders.IWritableFileProvider interface instead, by calling the GetWritableFileProvider method.

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