FindFile Method (IEasyUAFileTransfer)

Visual Basic
C#
C++/CLI

'Declaration
 
<CanBeNullAttribute()>
Function FindFile( _
   ByVal endpointDescriptor As UAEndpointDescriptor, _
   ByVal directoryNodeDescriptor As UANodeDescriptor, _
   ByVal fileName As String _
) As UANodeDescriptor

'Usage
 
Dim instance As IEasyUAFileTransfer
Dim endpointDescriptor As UAEndpointDescriptor
Dim directoryNodeDescriptor As UANodeDescriptor
Dim fileName As String
Dim value As UANodeDescriptor
 
value = instance.FindFile(endpointDescriptor, directoryNodeDescriptor, fileName)

[CanBeNull()]
UANodeDescriptor FindFile( 
   UAEndpointDescriptor endpointDescriptor,
   UANodeDescriptor directoryNodeDescriptor,
   string fileName
)

[CanBeNull()]
UANodeDescriptor^ FindFile( 
   UAEndpointDescriptor^ endpointDescriptor,
   UANodeDescriptor^ directoryNodeDescriptor,
   String^ fileName
)

Parameters

endpointDescriptor: Endpoint descriptor. Identifies the OPC-UA server.
directoryNodeDescriptor: Node descriptor of the OPC UA directory.
fileName: The name of the file to find.

Return Value

Returns a node descriptor of the file object, if the file named exists under the parent directory specified by the . Returns null otherwise.

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.

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

If the directoryNodeDescriptor does not denote an existing node of the OpcLabs.EasyOpc.UA.AddressSpace.Standard.UAObjectTypeIds.FileDirectoryType object type, the method throws OpcLabs.EasyOpc.UA.OperationModel.UAException. If, however, the directoryNodeDescriptor denotes an existing directory node, but the file named fileName does not exist, the method returns null.

This method finds an OPC UA node of object type FileType, which is described here: . The organization of files under directories is described here: . Files are referenced from their parent directory using the OpcLabs.EasyOpc.UA.AddressSpace.Standard.UAReferenceTypeIds.Organizes reference type.

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

Reference

IEasyUAFileTransfer Interface
IEasyUAFileTransfer Members
FindDirectory Method
FindFile(IEasyUAFileTransfer,UAEndpointDescriptor,UANamedNodeDescriptor) Method
GetFile(IEasyUAFileTransfer,UAEndpointDescriptor,UANamedNodeDescriptor) Method
IsFile Method
ListFileNames Method