OPC Studio User's Guide and Reference
FindFile Method (IEasyUAFileTransfer)



OpcLabs.EasyOpcUA Assembly > OpcLabs.EasyOpc.UA.FileTransfer Namespace > IEasyUAFileTransfer Interface : FindFile Method
Endpoint descriptor. Identifies the OPC-UA server.
Node descriptor of the OPC UA directory.
The name of the file to find.
Finds a file object with the given name under the specified parent directory.
Syntax
'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)

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 fileName exists under the parent directory specified by the directoryNodeDescriptor. Returns null otherwise.
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.

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.

Remarks

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.

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