Installed Examples - Web - WebApplication1

The simplest ASP.NET Web application for OPC “Classic”. Reads and displays an OPC item value.

The default page code-behind:

C#
VB.NET

// $Header: $
// Copyright (c) CODE Consulting and Development, s.r.o., Plzen. All rights reserved.

// ReSharper disable ArrangeModifiersOrder
// ReSharper disable InconsistentNaming

//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-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 OpcLabs.EasyOpc.DataAccess;
using System;
using OpcLabs.EasyOpc.DataAccess.Extensions;
using OpcLabs.EasyOpc.OperationModel;

namespace WebApplication1
{
    public partial class _Default : System.Web.UI.Page
    {
        static _Default()
        {
            // Enable auto-subscribing optimization (not necessary), which can improve performance with repeated Read requests.
            Client.TryEnableAutoSubscribingOptimization();
        }

        // Use a shared client instance to allow for better optimization.
        static private readonly EasyDAClient Client = new EasyDAClient();

        protected void Page_Load(object sender, EventArgs e)
        {
            try
            {
                object value = Client.ReadItemValue("", "OPCLabs.KitServer.2", "Demo.Single");
                TextBox1.Text = value?.ToString() ?? "";
            }
            catch (OpcException opcException)
            {
                TextBox1.Text = $"*** {opcException.Message}";
            }
        }
    }
}

' $Header: $
' Copyright (c) CODE Consulting and Development, s.r.o., Plzen. All rights reserved.

'
' 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 OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.DataAccess.Extensions
Imports OpcLabs.EasyOpc.OperationModel

' ReSharper disable InconsistentNaming

Partial Public Class _Default
    Inherits Page

    Shared Sub New()
        ' Enable auto-subscribing optimization (not necessary), which can improve performance with repeated Read requests.
        Client.TryEnableAutoSubscribingOptimization()
    End Sub

    ' Use a shared client instance to allow for better optimization.
    Shared ReadOnly Client As New EasyDAClient

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
        Try
            Dim value As Object = Client.ReadItemValue("", "OPCLabs.KitServer.2", "Demo.Single")
            TextBox1.Text = value
        Catch opcException As OpcException
            TextBox1.Text = $"*** {opcException.Message}"
        End Try
    End Sub

End Class

Conceptual

Examples for OPC “Classic” (OPC-DA, OPC XML-DA and OPC-A&E)

Reading just the value (OPC Classic)