OpenOrCreateStream(IEasyUAFileTransfer,UAEndpointDescriptor,UANamedNodeDescriptor,FileMode,FileAccess) Method

Opens or creates an OPC UA file, and returns a System.IO.Stream, specifying the file mode, and file access flags.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<ExtensionAttribute()>
<NotNullAttribute()>
Public Overloads Shared Function OpenOrCreateStream( _
   ByVal fileTransfer As IEasyUAFileTransfer, _
   ByVal endpointDescriptor As UAEndpointDescriptor, _
   ByVal fileNamedNodeDescriptor As UANamedNodeDescriptor, _
   ByVal fileMode As FileMode, _
   ByVal fileAccess As FileAccess _
) As Stream

'Usage
 
Dim fileTransfer As IEasyUAFileTransfer
Dim endpointDescriptor As UAEndpointDescriptor
Dim fileNamedNodeDescriptor As UANamedNodeDescriptor
Dim fileMode As FileMode
Dim fileAccess As FileAccess
Dim value As Stream
 
value = IEasyUAFileTransferExtension2.OpenOrCreateStream(fileTransfer, endpointDescriptor, fileNamedNodeDescriptor, fileMode, fileAccess)

[Extension()]
[NotNull()]
public static Stream OpenOrCreateStream( 
   IEasyUAFileTransfer fileTransfer,
   UAEndpointDescriptor endpointDescriptor,
   UANamedNodeDescriptor fileNamedNodeDescriptor,
   FileMode fileMode,
   FileAccess fileAccess
)

[Extension()]
[NotNull()]
public:
static Stream^ OpenOrCreateStream( 
   IEasyUAFileTransfer^ fileTransfer,
   UAEndpointDescriptor^ endpointDescriptor,
   UANamedNodeDescriptor^ fileNamedNodeDescriptor,
   FileMode fileMode,
   FileAccess fileAccess
)

Parameters

fileTransfer

The OPC UA file transfer object that will perform the operation.

This is typically the OpcLabs.EasyOpc.UA.FileTransfer.EasyUAFileTransferClient object.

The value of this parameter cannot be null (Nothing in Visual Basic).

endpointDescriptor

Endpoint descriptor. Identifies the OPC-UA server.

Because the OpcLabs.EasyOpc.UA.UAEndpointDescriptor has implicit conversions from System.String and System.Uri, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a string (representing the endpoint URL, or a so-called OPC UA endpoint descriptor string), or a System.Uri object, in place of this parameter, and the corresponding endpoint descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the OpcLabs.EasyOpc.UA.UAEndpointDescriptor.FromString or OpcLabs.EasyOpc.UA.UAEndpointDescriptor.FromUri static method instead.

If you are using OPC Wizard (for server development), an implicit conversion from OpcLabs.EasyOpc.UA.EasyUAServerCore can be used in the same way to simply pass the server object in place of this parameter, which will use its OpcLabs.EasyOpc.UA.EasyUAServerCore.EffectiveServerDescriptor property for the connection.

The value of this parameter cannot be null (Nothing in Visual Basic).

fileNamedNodeDescriptor

The named node descriptor of the file on which the stream should be opened or that should be created for the stream.

Because the OpcLabs.EasyOpc.UA.Navigation.UANamedNodeDescriptor has an implicit conversion from OpcLabs.EasyOpc.UA.UANodeDescriptor, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a OpcLabs.EasyOpc.UA.UANodeDescriptor (containing the final node descriptor) in place of this parameter, and the corresponding OPC UA named node descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the OpcLabs.EasyOpc.UA.Navigation.UANamedNodeDescriptor.FromUANodeDescriptor static method instead.

The value of this parameter cannot be null (Nothing in Visual Basic).

fileMode

One of the enumeration values that determines how to open or create the file.

fileAccess

A bitwise combination of the enumeration values that sets the System.IO.Stream.CanRead and System.IO.Stream.CanWrite properties of the System.IO.Stream object.

Return Value

Returns a System.IO.Stream opened for access to the specified file.

This method never returns null (Nothing in Visual Basic).

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.FileNotFoundException	An attempt to access a file that does not exist on disk has failed. 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.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.

Remarks

See OPC UA File Transfer internals for information about Stream buffering and Stream expansion.

CAUTION: This method does not throw the usual OpcLabs.EasyOpc.UA.OperationModel.UAException. Instead, an System.IO.IOException is thrown in case of an error during the operation.

For this method to succeed if it is creating a new file, the fileNamedNodeDescriptor must contain both the named node path (of the parent directory) in the OpcLabs.EasyOpc.UA.Navigation.UANamedNodeDescriptor.NamedNodePath property, and the node name (name of the file) in the OpcLabs.EasyOpc.UA.Navigation.UANamedNodeDescriptor.NodeName property. If this method is opening an existing stream, the file can also be specified using just the final node descriptor (node of the file object) in the OpcLabs.EasyOpc.UA.Navigation.UANamedNodeDescriptor.FinalNodeDescriptor property.

Recommendation: Whenever possible, do not use this method directly, and use a higher-level abstraction instead. You can obtain a writable file provider (using GetWritableFileProvider), and make use of its methods, and methods available on the writable directory contents (obtained using OpcLabs.BaseLib.Extensions.FileProviders.IWritableDirectory.GetWritableDirectoryContents) or writable file info (obtained using OpcLabs.BaseLib.Extensions.FileProviders.IWritableDirectory.GetWritableFileInfo).

This is an extension method (info: C#, VB.NET). In languages that have support for extensions methods (such as C# and VB.NET), you can use the extension method as if it were a regular method on the object that is its first parameter. In other languages (such as with Python.NET), you will call the extension as a static method, and pass it the object on which it acts as its first parameter.

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

IEasyUAFileTransferExtension2 Class
IEasyUAFileTransferExtension2 Members
Overload List
CreateStream(IEasyUAFileTransfer,UAEndpointDescriptor,UANamedNodeDescriptor) Method
OpenOrCreateStreamWriter(IEasyUAFileTransfer,UAEndpointDescriptor,UANamedNodeDescriptor) Method
OpenStream(IEasyUAFileTransfer,UAEndpointDescriptor,UANamedNodeDescriptor) Method

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