UADataVariableExtension Class

Contains extension methods to the UADataVariable class.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<ExtensionAttribute()>
<ExceptionContractAnnotationAttribute(True)>
Public MustInherit NotInheritable Class UADataVariableExtension

'Usage
 
Dim instance As UADataVariableExtension

[Extension()]
[ExceptionContractAnnotation(true)]
public static class UADataVariableExtension

[Extension()]
[ExceptionContractAnnotation(true)]
public ref class UADataVariableExtension abstract sealed

Remarks

NOTE: This class is intentionally *not* placed in the Extensions namespace, but rather alongside the extendee. The extension methods in this class are commonly used, and from the point of view of the developer, can be considered as part of the class. In addition, this placement allows fewer namespaces references in typical projects, and better consistency with the COM interfaces (as only methods from this extension class may appear in the COM interfaces).

Other extension classes may exist as well.

This class contains extension methods (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.

Example

CSharp
VB.NET

// This example shows how to create a data variable and implement reading its value using a function.
// 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 ReadValueFunction
    {
        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 data variable, defining its read values by a function.
            // The type of the data variable (Int32, in this case) is inferred from the type returned by the function.
            var random = new Random();
            server.Add(new UADataVariable("ReadThisVariable").ReadValueFunction(() => random.Next()));

            // 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.");
        }
    }
}

' This example shows how to create a data variable and implement reading its value using a function.
' 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 ReadValueFunction
        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 data variable, defining its read values by a function.
            ' The type of the data variable (Int32, in this case) is inferred from the type returned by the function.
            Dim random = New Random()
            server.Add(New UADataVariable("ReadThisVariable").ReadValueFunction(Function() random.Next()))

            ' 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
    End Class
End Namespace

Inheritance Hierarchy

System.Object
OpcLabs.EasyOpc.UA.NodeSpace.UADataVariableExtension

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

UADataVariableExtension Members
OpcLabs.EasyOpc.UA.NodeSpace Namespace

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