Installed Examples - Console - SubscribeFromXml

Loads a list of OPC "Classic" items from an XML file and subscribes to them.

The main program:

C#
VB.NET

// This example shows how to load a list of OPC "Classic" items from an XML file and subscribe to them.

using System;
using System.Threading;
using System.Xml;
using System.Xml.Serialization;
using OpcLabs.BaseLib.Runtime.InteropServices;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.OperationModel;

namespace SubscribeFromXml
{
    class Program
    {
        static void Main()
        {
            ComManagement.Instance.AssureSecurityInitialization();

            Console.WriteLine("Loading items from XML file...");
            var xmlSerializer = new XmlSerializer(typeof(DAItemGroupArguments[]));
            var xmlReader = XmlReader.Create("OpcItems.xml", new XmlReaderSettings {IgnoreWhitespace = true});
            var argArray = (DAItemGroupArguments[]) (xmlSerializer.Deserialize(xmlReader));

            if (!(argArray is null))
            {
                Console.WriteLine();
                Console.WriteLine("Arguments loaded:");
                foreach (DAItemGroupArguments itemGroupArguments in argArray)
                    Console.WriteLine($"  {itemGroupArguments}");

                Console.WriteLine();
                Console.WriteLine("Subscribing for 30 seconds...");
                EasyDAClient.SharedInstance.SubscribeMultipleItems(argArray,
                    (_, eventArgs) => Console.WriteLine(
                        $"[{eventArgs.Arguments.State}] {eventArgs.Arguments.ItemDescriptor.ItemId}: {eventArgs.Vtq}"));
                Thread.Sleep(30 * 1000);

                Console.WriteLine();
                Console.WriteLine("Unsubscribing...");
                EasyDAClient.SharedInstance.UnsubscribeAllItems();
            }

            Console.WriteLine();
            Console.WriteLine("Finished.");
        }
    }
}

Imports System.Threading
Imports System.Xml
Imports System.Xml.Serialization
Imports OpcLabs.BaseLib.Runtime.InteropServices
Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.DataAccess.OperationModel


Friend Class Program
    Shared WithEvents _client As New EasyDAClient

    <MTAThread> ' needed for COM security initialization to succeed
    Shared Sub Main()
        ComManagement.Instance.AssureSecurityInitialization()

        Console.WriteLine("Loading items from XML file...")
        Dim xmlSerializer = New XmlSerializer(GetType(DAItemGroupArguments()))
        Dim xmlReader = Xml.XmlReader.Create("OpcItems.xml", New XmlReaderSettings With {.IgnoreWhitespace = True})
        Dim argArray = CType(xmlSerializer.Deserialize(xmlReader), DAItemGroupArguments())

        If argArray IsNot Nothing Then
            Console.WriteLine("Subscribing for 30 seconds...")
            _client.SubscribeMultipleItems(argArray)
            Thread.Sleep(30 * 1000)

            Console.WriteLine("Unsubscribing...")
            _client.UnsubscribeAllItems()
        End If

        Console.WriteLine("Finished.")
    End Sub

    Private Shared Sub ItemChanged(ByVal sender As Object, ByVal eventArgs As EasyDAItemChangedEventArgs) Handles _client.ItemChanged
        Console.WriteLine("{0}: {1}", eventArgs.Arguments.ItemDescriptor.ItemId, eventArgs.Vtq)
    End Sub
End Class

The XML file with list of items:

<?xml version="1.0" encoding="utf-8"?>
<!-- This file specifies the OPC items to be subscribed to, and their associated state objects (integers, in this case). -->
<ArrayOfDAItemGroupArguments xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <DAItemGroupArguments>
    <State xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.BaseLib.OperationModel">
      <TypeFullName xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.BaseLib.Xml">System.Int32</TypeFullName>
      <Instance xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.BaseLib.Xml">1</Instance>
    </State>
    <ServerDescriptor xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.EasyOpc.DataAccess.OperationModel">
      <UrlString xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.BaseLib">opcda:OPCLabs.KitServer.2</UrlString>
    </ServerDescriptor>
    <ItemDescriptor xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.EasyOpc.DataAccess.OperationModel">
      <NodeId xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.EasyOpc">Simulation.Random</NodeId>
    </ItemDescriptor>
    <GroupParameters xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.EasyOpc.DataAccess.OperationModel">
      <RequestedUpdateRate xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.EasyOpc.DataAccess">1000</RequestedUpdateRate>
      <PercentDeadband xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.EasyOpc.DataAccess">0.0</PercentDeadband>
    </GroupParameters>
  </DAItemGroupArguments>
  <DAItemGroupArguments>
    <State xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.BaseLib.OperationModel">
      <TypeFullName xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.BaseLib.Xml">System.Int32</TypeFullName>
      <Instance xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.BaseLib.Xml">2</Instance>
    </State>
    <ServerDescriptor xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.EasyOpc.DataAccess.OperationModel">
      <UrlString xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.BaseLib">opcda:OPCLabs.KitServer.2</UrlString>
    </ServerDescriptor>
    <ItemDescriptor xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.EasyOpc.DataAccess.OperationModel">
      <NodeId xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.EasyOpc">Simulation.Ramp (10 s)</NodeId>
    </ItemDescriptor>
    <GroupParameters xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.EasyOpc.DataAccess.OperationModel">
      <RequestedUpdateRate xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.EasyOpc.DataAccess">1000</RequestedUpdateRate>
      <PercentDeadband xmlns="http://schemas.datacontract.org/2004/07/OpcLabs.EasyOpc.DataAccess">0.0</PercentDeadband>
    </GroupParameters>
  </DAItemGroupArguments>
</ArrayOfDAItemGroupArguments>

Conceptual

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

Subscribing to OPC Classic Items