Examples - OPC Data Access - Read while subscribed

// This example shows how to read items while subscribed.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

using System;
using System.Diagnostics;
using System.Threading;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.OperationModel;

namespace DocExamples.DataAccess._EasyDAClient
{
    partial class SubscribeMultipleItems
    {
        public static void WithRead()
        {
            // Instantiate the client object.
            using (var client = new EasyDAClient())
            {
                client.ItemChanged += client_Read_ItemChanged;

                Console.WriteLine("Subscribing item changes...");
                client.SubscribeMultipleItems(
                    new[] {
                            new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, null), 
                            new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Sine (1 min)", 1000, null),  
                        });

                Console.WriteLine("Waiting for 10 seconds...");
                Thread.Sleep(10 * 1000);

                Console.WriteLine("Reading items...");
                DAVtqResult[] vtqResults = client.ReadMultipleItems("OPCLabs.KitServer.2",
                    new DAItemDescriptor[]
                    {
                        "Trends.Ramp (1 min)", "Trends.Sine (1 min)"
                    });

                for (int i = 0; i < vtqResults.Length; i++)
                {
                    Debug.Assert(vtqResults[i] != null);

                    if (vtqResults[i].Succeeded)
                        Console.WriteLine("vtqResults[{0}].Vtq: {1}", i, vtqResults[i].Vtq);
                    else
                        Console.WriteLine("vtqResults[{0}] *** Failure: {1}", i, vtqResults[i].ErrorMessageBrief);
                }

                Console.WriteLine("Waiting for 10 seconds...");
                Thread.Sleep(10 * 1000);

                Console.WriteLine("Unsubscribing item changes...");
            }

            Console.WriteLine("Finished.");
        }

        // Item changed event handler
        static void client_Read_ItemChanged(object sender, EasyDAItemChangedEventArgs e)
        {
            if (e.Succeeded)
                Console.WriteLine($"< {e.Arguments.ItemDescriptor.ItemId}: {e.Vtq}");
            else
                Console.WriteLine($"< {e.Arguments.ItemDescriptor.ItemId} *** Failure: {e.ErrorMessageBrief}");
        }
    }
}

# This example shows how to read items while subscribed.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python .
# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc
import time

# Import .NET namespaces.
from OpcLabs.EasyOpc import *
from OpcLabs.EasyOpc.DataAccess import *
from OpcLabs.EasyOpc.DataAccess.OperationModel import *


# Item changed event handler.
def itemChanged(sender, e):
    if e.Succeeded:
        print('< ', e.Arguments.ItemDescriptor.ItemId, ': ', e.Vtq, sep='')
    else:
        print('< ', e.Arguments.ItemDescriptor.ItemId, ' *** Failure: ', e.ErrorMessageBrief, sep='')


# Instantiate the client object.
client = EasyDAClient()

client.ItemChanged += itemChanged

print('Subscribing item changes...')
client.SubscribeMultipleItems([
    EasyDAItemSubscriptionArguments('', 'OPCLabs.KitServer.2', 'Simulation.Random', 1000, None),
    EasyDAItemSubscriptionArguments('', 'OPCLabs.KitServer.2', 'Trends.Sine (1 min)', 1000, None),
    ])

print('Processing item change notifications for 10 seconds...')
time.sleep(10)

print('Reading items...')
vtqResultArray = client.ReadMultipleItems([
    DAReadItemArguments(ServerDescriptor('OPCLabs.KitServer.2'), DAItemDescriptor('Trends.Ramp (1 min)')),
    DAReadItemArguments(ServerDescriptor('OPCLabs.KitServer.2'), DAItemDescriptor('Trends.Sine (1 min)')),
    ])

for i, vtqResult in enumerate(vtqResultArray):
    assert vtqResult is not None
    if vtqResult.Succeeded:
        print('vtqResultArray[', i, '].Vtq: ', vtqResult.Vtq, sep='')
    else:
        print('vtqResultArray[', i, '] *** Failure: ', vtqResult.ErrorMessageBrief, sep='')

print('Processing item change notifications for 10 seconds...')
time.sleep(10)

print('Unsubscribing all items...')
client.UnsubscribeAllItems()

client.ItemChanged -= itemChanged

print('Finished.')

' This example shows how to read items while subscribed.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

Imports System.Threading
Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.DataAccess.OperationModel

Namespace DataAccess._EasyDAClient
    Partial Friend Class SubscribeMultipleItems
        Public Shared Sub WithRead()
            ' Instantiate the client object.
            Using client = New EasyDAClient()
                AddHandler client.ItemChanged, AddressOf client_Read_ItemChanged

                Console.WriteLine("Subscribing item changes...")
                Dim handleArray() As Integer = client.SubscribeMultipleItems(New DAItemGroupArguments() {
                    New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, Nothing),
                    New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Sine (1 min)", 1000, Nothing)
                })

                Console.WriteLine("Waiting for 10 seconds...")
                Thread.Sleep(10 * 1000)

                Console.WriteLine("Reading items...")
                Dim vtqResults() As DAVtqResult = client.ReadMultipleItems("OPCLabs.KitServer.2",
                    New DAItemDescriptor() {"Trends.Ramp (1 min)", "Trends.Sine (1 min)"})

                For i = 0 To vtqResults.Length - 1
                    Debug.Assert(vtqResults(i) IsNot Nothing)

                    If vtqResults(i).Succeeded Then
                        Console.WriteLine("vtqResult[{0}].Vtq: {1}", i, vtqResults(i).Vtq)
                    Else
                        Console.WriteLine("vtqResult[{0}] *** Failure: {1}", i, vtqResults(i).ErrorMessageBrief)
                    End If
                Next i

                Console.WriteLine("Waiting for 10 seconds...")
                Thread.Sleep(10 * 1000)

                Console.WriteLine("Unsubscribing item changes...")
            End Using

            Console.WriteLine("Finished.")
        End Sub

        ' Item changed event handler
        Private Shared Sub client_Read_ItemChanged(ByVal sender As Object, ByVal e As EasyDAItemChangedEventArgs)
            If e.Succeeded Then
                Console.WriteLine($"< {e.Arguments.ItemDescriptor.ItemId}: {e.Vtq}")
            Else
                Console.WriteLine($"< {e.Arguments.ItemDescriptor.ItemId} *** Failure: {e.ErrorMessageBrief}")
            End If
        End Sub
    End Class
End Namespace

Conceptual

Reading from OPC Classic Items

Examples - OPC Unified Architecture

Examples - OPC Unified Architecture - Read multiple nodes or attributes