Examples - Server OPC UA - Access parent node and use its data

.NET

C#
VB.NET

// This example shows how data from parent node can be used in the read event 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 ParentNode
    {
        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 multiple folder nodes, each with a data variable in it. Distinguish the folders by their state, however
            // the data variables are constructed the same, and use the same read event handler.

            UAFolder myFolder1 = UAFolder.CreateIn(server.Objects, "MyFolder1").SetState(1);
            UADataVariable.CreateIn(myFolder1, "MyDataVariable").Read += MyDataVariableOnRead;

            UAFolder myFolder2 = UAFolder.CreateIn(server.Objects, "MyFolder2").SetState(2);
            UADataVariable.CreateIn(myFolder2, "MyDataVariable").Read += MyDataVariableOnRead;

            UAFolder myFolder3 = UAFolder.CreateIn(server.Objects, "MyFolder3").SetState(3);
            UADataVariable.CreateIn(myFolder3, "MyDataVariable").Read += MyDataVariableOnRead;

            UAFolder myFolder4 = UAFolder.CreateIn(server.Objects, "MyFolder4").SetState(4);
            UADataVariable.CreateIn(myFolder4, "MyDataVariable").Read += MyDataVariableOnRead;

            UAFolder myFolder5 = UAFolder.CreateIn(server.Objects, "MyFolder5").SetState(5);
            UADataVariable.CreateIn(myFolder5, "MyDataVariable").Read += MyDataVariableOnRead;

            // 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 read event on the data variable. 
        /// </summary>
        /// <param name="sender">The data variable object that sends the event.</param>
        /// <param name="e">Data for the variable read event.</param>
        static private void MyDataVariableOnRead(object sender, UADataVariableReadEventArgs e)
        {
            // Obtain the parent folder of the data variable that is being read.
            UAServerNode parentNode = e.DataVariable.ParentNode;

            // Obtain the state associated with the folder, where the data variable is located.
            // Use it as the offset for the random value, so that each data variable generates values in a unique range.
            int offset = (int)parentNode.State*100;

            // Generate a random value, indicate that the read has been handled, and return the generated value.
            e.HandleAndReturn(Random.Next(offset, offset + 100));
        }

        static private readonly Random Random = new Random();
    }
}

' This example shows how data from parent node can be used in the read event 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 ParentNode
        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 multiple folder nodes, each with a data variable in it. Distinguish the folders by their state, however
            ' the data variables are constructed the same, and use the same read event handler.

            Dim myFolder1 As UAFolder = UAFolder.CreateIn(server.Objects, "MyFolder1").SetState(1)
            AddHandler UADataVariable.CreateIn(myFolder1, "MyDataVariable").Read, AddressOf MyDataVariableOnRead

            Dim myFolder2 As UAFolder = UAFolder.CreateIn(server.Objects, "MyFolder2").SetState(2)
            AddHandler UADataVariable.CreateIn(myFolder2, "MyDataVariable").Read, AddressOf MyDataVariableOnRead

            Dim myFolder3 As UAFolder = UAFolder.CreateIn(server.Objects, "MyFolder3").SetState(3)
            AddHandler UADataVariable.CreateIn(myFolder3, "MyDataVariable").Read, AddressOf MyDataVariableOnRead

            Dim myFolder4 As UAFolder = UAFolder.CreateIn(server.Objects, "MyFolder4").SetState(4)
            AddHandler UADataVariable.CreateIn(myFolder4, "MyDataVariable").Read, AddressOf MyDataVariableOnRead

            Dim myFolder5 As UAFolder = UAFolder.CreateIn(server.Objects, "MyFolder5").SetState(5)
            AddHandler UADataVariable.CreateIn(myFolder5, "MyDataVariable").Read, AddressOf MyDataVariableOnRead

            ' 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 read event on the data variable. 
        ''' </summary>
        ''' <param name="sender">The data variable object that sends the event.</param>
        ''' <param name="e">Data for the variable read event.</param>
        Private Shared Sub MyDataVariableOnRead(ByVal sender As Object, ByVal e As UADataVariableReadEventArgs)
            ' Obtain the parent folder of the data variable that is being read.
            Dim parentNode As UAServerNode = e.DataVariable.ParentNode

            ' Obtain the state associated with the folder, where the data variable is located.
            ' Use it as the offset for the random value, so that each data variable generates values in a unique range.
            Dim offset As Integer = CInt(parentNode.State * 100)

            ' Generate a random value, indicate that the read has been handled, and return the generated value.
            e.HandleAndReturn(Random.Next(offset, offset + 100))
        End Sub

        Private Shared ReadOnly Random As Random = New Random()
    End Class
End Namespace

Concepts

Pull Data Provision Model

Fundamentals

OPC Wizard Node Objects