OPC Studio User's Guide and Reference
ProcessWrite Method



OpcLabs.ServerOpcUA Assembly > OpcLabs.EasyOpc.UA.NodeSpace Namespace > UADataVariableExtension Class : ProcessWrite Method
The data variable that will be modified and returned.

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

The write function, i.e. the function that accepts the attribute data to be written, performs the write operation, and returns the status code that is the result of the OPC UA Write.

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

Specifies that writes of this data variable will be processed by the specified write function.
Syntax
'Declaration
 
<ExtensionAttribute()>
<NotNullAttribute()>
Public Shared Function ProcessWrite( _
   ByVal dataVariable As UADataVariable, _
   ByVal writeFunction As Func(Of UAAttributeData,UAStatusCode) _
) As UADataVariable
'Usage
 
Dim dataVariable As UADataVariable
Dim writeFunction As Func(Of UAAttributeData,UAStatusCode)
Dim value As UADataVariable
 
value = UADataVariableExtension.ProcessWrite(dataVariable, writeFunction)

Parameters

dataVariable
The data variable that will be modified and returned.

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

writeFunction
The write function, i.e. the function that accepts the attribute data to be written, performs the write operation, and returns the status code that is the result of the OPC UA Write.

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

Return Value

Returns the dataVariable, internally modified as defined by the method.

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

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 works by adding an event handler to the Write event of the data variable.

The specified write function is used to process the writes for this data variable only, i.e. not for any of its children. This is achieved by setting the UADataVariable.HandleChildNodes property to false (which you can revert if needed), and also by checking whether the data variable to be processed by the event is this data variable.

The writeFunction is allowed to return null, which is interpreted as a "Good" status code.

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

See Also