Write Event (EasyUAServerCore)

Raised to supply the OPC UA write data.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
Public Event Write As UADataVariableWriteEventHandler

'Usage
 
Dim instance As EasyUAServerCore
Dim handler As UADataVariableWriteEventHandler
 
AddHandler instance.Write, handler

public event UADataVariableWriteEventHandler Write

public:
event UADataVariableWriteEventHandler^ Write

Event Data

The event handler receives an argument of type UADataVariableWriteEventArgs containing data related to this event. The following UADataVariableWriteEventArgs properties provide information specific to this event.

Property	Description
AttributeData	The value/timestamps/status code that is the input of the OPC UA write.
DataVariable	The data variable being processed. (Inherited from OpcLabs.EasyOpc.UA.OperationModel.UADataVariableProcessedEventArgs)
Handled	(Inherited from System.ComponentModel.HandledEventArgs)
Result	The status code that is the result of the OPC UA write.

Remarks

This event is triggered when data is requested to be written to the OPC UA server. Event handlers attached to this event are expected to consume the data of the write operation. It is a crucial mechanism for custom data consumption in response to OPC client write requests.

The event handlers for this event should not throw any exceptions. If an exception is thrown from the event handler, it might be reported through debugging, tracing or logging facilities, but the processing continues as normally, i.e. the invocation of remaining handlers, and the outcome of the Write operation, are not influenced.

Example

CSharp
VB.NET

// This example shows how to handle the write event on a folder, providing a way to implement writing of multiple data
// variables using a single handler.
// 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.BaseLib.NodeSpace;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.NodeSpace;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UAServerDocExamples._UAServerNode
{
    class Write
    {
        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 folder node.
            UAFolder myFolder = UAFolder.CreateIn(server.Objects, "MyFolder");

            // Create data variables in the folder. Distinguish them by their state.
            myFolder.Add(new UADataVariable("MyDataVariable1").ValueType<int>().SetState(1));
            myFolder.Add(new UADataVariable("MyDataVariable2").ValueType<int>().SetState(2));
            myFolder.Add(new UADataVariable("MyDataVariable3").ValueType<int>().SetState(3));
            myFolder.Add(new UADataVariable("MyDataVariable4").ValueType<int>().SetState(4));
            myFolder.Add(new UADataVariable("MyDataVariable5").ValueType<int>().SetState(5));

            // Handle the write event for the folder.
            myFolder.Write += MyFolderOnWrite;

            // Start the server.
            Console.WriteLine("The server is starting...");
            server.Start();

            Console.WriteLine("The server is started.");
            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.");
        }

        /// <summary>
        /// Event handler for the write event on the folder. 
        /// </summary>
        /// <param name="sender">The folder object that sends the event.</param>
        /// <param name="e">Data for the variable write event.</param>
        static private void MyFolderOnWrite(object sender, UADataVariableWriteEventArgs e)
        {
            // Obtain the state associated with the data variable that is being written, and display it on the console
            // together with the new value.
            Console.WriteLine($"Data variable {e.DataVariable.State}, value written: {e.AttributeData.Value}");
        }
    }
}

' This example shows how to handle the write event on a folder, providing a way to implement writing of multiple data
' variables using a single handler.
' 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.BaseLib.NodeSpace
Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.NodeSpace
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace _UAServerNode
    Partial Friend Class Write
        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 folder node.
            Dim myFolder As UAFolder = UAFolder.CreateIn(server.Objects, "MyFolder")

            ' Create data variables in the folder. Distinguish them by their state.
            myFolder.Add(New UADataVariable("MyDataVariable1").ValueType(Of Integer)().SetState(1))
            myFolder.Add(New UADataVariable("MyDataVariable2").ValueType(Of Integer)().SetState(2))
            myFolder.Add(New UADataVariable("MyDataVariable3").ValueType(Of Integer)().SetState(3))
            myFolder.Add(New UADataVariable("MyDataVariable4").ValueType(Of Integer)().SetState(4))
            myFolder.Add(New UADataVariable("MyDataVariable5").ValueType(Of Integer)().SetState(5))

            ' Handle the read event for the folder.
            AddHandler myFolder.Write, AddressOf MyFolderOnWrite

            ' Start the server.
            Console.WriteLine("The server is starting...")
            server.Start()

            Console.WriteLine("The server is started.")
            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

        ''' <summary>
        ''' Event handler for the write event on the folder.  
        ''' </summary>
        ''' <param name="sender">The data variable object that sends the event.</param>
        ''' <param name="e">Data for the variable write event.</param>
        Private Shared Sub MyFolderOnWrite(ByVal sender As Object, ByVal e As UADataVariableWriteEventArgs)
            ' Obtain the state associated with the data variable that is being written, and display it on the console
            ' together with the new value.
            Console.WriteLine($"Data variable {e.DataVariable.State}, value written: {e.AttributeData.Value}")
        End Sub

        Private Shared ReadOnly Random As Random = New Random()
    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

Reference

EasyUAServerCore Class
EasyUAServerCore Members

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