Makes data variable that consumes typed attribute data using the write function.
Syntax
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).
Type Parameters
- TValue
- The type of the value of the data variable.
Return Value
Returns the , internally modified as defined by the method.
This method never returns null
(Nothing
in Visual Basic).
Exceptions
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. |
Example
// This example shows how to use a function to define what happens with the attribute data when an OPC client writes to a
// data variable. This is an example of the push data consumption model.
// You can use any OPC UA client, including our Connectivity Explorer and OpcCmd utility, to connect to the server.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client, server and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-OPCStudio-CSharp .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.
using System;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.NodeSpace;
namespace UAServerDocExamples._UADataVariable
{
partial class WriteFunction
{
public static void Main1()
{
// Instantiate the server object.
// By default, the server will run on endpoint URL "opc.tcp://localhost:48040/".
var server = new EasyUAServer();
// Create a writable data variable and add a function that will be called when the data variable is written to.
// The function returns a status code that indicates the outcome of the Write operation. We have chosen to only
// allow "Good" and "Uncertain", non-negative values to be written to the variable.
server.Add(new UADataVariable("WriteToThisVariable").WriteFunction<int>(
data =>
{
if (data.StatusCode.IsBad || (data.TypedValue < 0))
{
Console.WriteLine($"Attribute data rejected: {data}");
return UACodeBits.BadOutOfRange;
}
Console.WriteLine($"Attribute data written: {data}");
return null; // "Good"
}));
// Start the server.
Console.WriteLine("The server is starting...");
server.Start();
Console.WriteLine("The server is started.");
Console.WriteLine("Any value written to the example data variable will be displayed on the console.");
Console.WriteLine();
// Let the user decide when to stop.
Console.WriteLine("Press Enter to stop the server...");
Console.ReadLine();
// Stop the server.
Console.WriteLine("The server is stopping...");
server.Stop();
Console.WriteLine("The server is stopped.");
}
}
}
' This example shows how to use a function to define what happens with the attribute data when an OPC client writes to a
' data variable. This is an example of the push data consumption model.
' You can use any OPC UA client, including our Connectivity Explorer and OpcCmd utility, to connect to the server.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET .
' Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
' a commercial license in order to use Online Forums, and we reply to every post.
Imports System
Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.NodeSpace
Namespace _UADataVariable
Partial Friend Class WriteFunction
Shared Sub Main1()
' Instantiate the server object.
' By default, the server will run on endpoint URL "opc.tcp://localhost:48040/".
Dim server = New EasyUAServer()
' Create a writable data variable and add a function that will be called when the data variable is written to.
' The function returns a status code that indicates the outcome of the Write operation. We have chosen to only
' allow "Good" and "Uncertain", non-negative values to be written to the variable.
server.Add(New UADataVariable("WriteToThisVariable").WriteFunction(Of Integer)(
Function(data)
If data.StatusCode.IsBad OrElse (data.TypedValue < 0) Then
Console.WriteLine($"Attribute data rejected: {data}")
Return UACodeBits.BadOutOfRange
End If
Console.WriteLine($"Attribute data written: {data}")
Return Nothing ' "Good"
End Function
))
' Start the server.
Console.WriteLine("The server is starting...")
server.Start()
Console.WriteLine("The server is started.")
Console.WriteLine("Any value written to the example data variable will be displayed on the console.")
Console.WriteLine()
' Let the user decide when to stop.
Console.WriteLine("Press Enter to stop the server...")
Console.ReadLine()
' Stop the server.
Console.WriteLine("The server is stopping...")
server.Stop()
Console.WriteLine("The server is stopped.")
End Sub
End Class
End Namespace
// This example shows how to indicate that the write operation completes asynchronously. This is an example of the push
// data consumption model.
// You can use any OPC UA client, including our Connectivity Explorer and OpcCmd utility, to connect to the server.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client, server and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-OPCStudio-CSharp .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.
using System;
using System.Threading;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.NodeSpace;
namespace UAServerDocExamples._UADataVariable
{
partial class WriteFunction
{
public static void GoodCompletesAsynchronously()
{
// Instantiate the server object.
// By default, the server will run on endpoint URL "opc.tcp://localhost:48040/".
var server = new EasyUAServer();
// Create a writable data variable and add a function that will be called when the data variable is written to.
// The function returns a status code that indicates the outcome of the Write operation. Since we do not know the
// true outcome of the write operation at the time of the function call, we return status code
// "GoodCompletesAsynchronously".
server.Add(new UADataVariable("WriteToThisVariable").WriteFunction<int>(
data =>
{
// The actual write operation is performed asynchronously, on a separate thread.
var thread = new Thread(() => Console.WriteLine($"Attribute data written: {data}"));
thread.Start();
return UACodeBits.GoodCompletesAsynchronously;
}));
// Start the server.
Console.WriteLine("The server is starting...");
server.Start();
Console.WriteLine("The server is started.");
Console.WriteLine("Any value written to the example data variable will be displayed on the console.");
Console.WriteLine();
// Let the user decide when to stop.
Console.WriteLine("Press Enter to stop the server...");
Console.ReadLine();
// Stop the server.
Console.WriteLine("The server is stopping...");
server.Stop();
Console.WriteLine("The server is stopped.");
}
}
}
' This example shows how to indicate that the write operation completes asynchronously. This is an example of the push
' data consumption model.
' You can use any OPC UA client, including our Connectivity Explorer and OpcCmd utility, to connect to the server.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET .
' Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
' a commercial license in order to use Online Forums, and we reply to every post.
Imports System
Imports System.Threading
Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.NodeSpace
Namespace _UADataVariable
Partial Friend Class WriteFunction
Shared Sub GoodCompletesAsynchronously()
' Instantiate the server object.
' By default, the server will run on endpoint URL "opc.tcp://localhost:48040/".
Dim server = New EasyUAServer()
' Create a writable data variable and add a function that will be called when the data variable is written to.
' The function returns a status code that indicates the outcome of the Write operation. Since we do not know the
' true outcome of the write operation at the time of the function call, we return status code
' "GoodCompletesAsynchronously".
server.Add(New UADataVariable("WriteToThisVariable").WriteFunction(Of Integer)(
Function(data)
' The actual write operation Is performed asynchronously, on a separate thread.
Dim thread = New Thread(Sub() Console.WriteLine($"Attribute data written: {data}"))
thread.Start()
Return UACodeBits.GoodCompletesAsynchronously
End Function
))
' Start the server.
Console.WriteLine("The server is starting...")
server.Start()
Console.WriteLine("The server is started.")
Console.WriteLine("Any value written to the example data variable will be displayed on the console.")
Console.WriteLine()
' Let the user decide when to stop.
Console.WriteLine("Press Enter to stop the server...")
Console.ReadLine()
' Stop the server.
Console.WriteLine("The server is stopping...")
server.Stop()
Console.WriteLine("The server is stopped.")
End Sub
End Class
End Namespace
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