Examples - OPC Data Access - Subscribe to single item with percent deadband

.NET

C#
VB.NET

// This example shows how subscribe to changes of a single item with percent deadband.
//
// 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 System;
using System.Diagnostics;
using System.Threading;
using OpcLabs.BaseLib.ComInterop;
using OpcLabs.EasyOpc.DataAccess;

namespace DocExamples.DataAccess._EasyDAClient
{
    partial class SubscribeItem
    {
        public static void PercentDeadband()
        {
            // Instantiate the client object.
            var client = new EasyDAClient();

            const float percentDeadband = 5.0f;
            Console.WriteLine($"Subscribing with {percentDeadband}% deadband...");
            // The callback is a lambda expression the displays the value
            client.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Ramp 0:100 (10 s)", 
                VarTypes.Empty, requestedUpdateRate:100, percentDeadband:percentDeadband, 
                (sender, eventArgs) =>
                {
                    Debug.Assert(!(eventArgs is null));

                    if (eventArgs.Succeeded)
                    {
                        Debug.Assert(!(eventArgs.Vtq is null));
                        Console.WriteLine(eventArgs.Vtq.ToString());
                    }
                    else
                        Console.WriteLine("*** Failure: {0}", eventArgs.ErrorMessageBrief);
                },
                state:null);

            Console.WriteLine("Processing item changed events for 10 seconds...");
            Thread.Sleep(10 * 1000);

            Console.WriteLine("Unsubscribing...");
            client.UnsubscribeAllItems();

            Console.WriteLine("Waiting for 2 seconds...");
            Thread.Sleep(2 * 1000);
        }
    }
}

' This example shows how subscribe to changes of a single item with percent deadband.
'
' 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.BaseLib.ComInterop
Imports OpcLabs.EasyOpc.DataAccess

Namespace DataAccess._EasyDAClient
    Partial Friend Class SubscribeItem
        Shared Sub PercentDeadband()
            ' Instantiate the client object
            Dim client = New EasyDAClient()

            Const percentDeadband As Single = 5.0F
            Console.WriteLine("Subscribing with {0}% deadband...", percentDeadband)
            ' The callback is a lambda expression the displays the value
            client.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Ramp 0:100 (10 s)",
                VarTypes.Empty, requestedUpdateRate:=100, percentDeadband:=percentDeadband,
                    Sub(sender, eventArgs)
                        Debug.Assert(eventArgs IsNot Nothing)
                        If eventArgs.Succeeded Then
                            Debug.Assert(eventArgs.Vtq IsNot Nothing)
                            Console.WriteLine(eventArgs.Vtq.ToString())
                        Else
                            Console.WriteLine("*** Failure: {0}", eventArgs.ErrorMessageBrief)
                        End If
                    End Sub,
                    state:=Nothing)

            Console.WriteLine("Processing item changed events for 10 seconds...")
            Threading.Thread.Sleep(10 * 1000)

            Console.WriteLine("Unsubscribing...")
            client.UnsubscribeAllItems()

            Console.WriteLine("Waiting for 2 seconds...")
            Threading.Thread.Sleep(2 * 1000)
        End Sub
    End Class
End Namespace

Python

Python (.NET)

# This example shows how subscribe to changes of a single item with percent deadband.
#
# 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 .
# 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.
# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc
import time

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


# Item changed callback.
def itemChangedCallback(sender, e):
    assert e is not None
    if e.Succeeded:
        assert e.Vtq is not None
        print(e.Vtq)
    else:
        print('*** Failure: ', e.ErrorMessageBrief, sep='')


PERCENT_DEADBAND = 5.0

# Instantiate the client object.
client = EasyDAClient()

print('Subscribing item changes with ', PERCENT_DEADBAND, '% deadband...', sep='')
# The callback is a regular method that displays the value.
IEasyDAClientExtension.SubscribeItem(client,
                                     '', 'OPCLabs.KitServer.2', 'Simulation.Ramp 0:100 (10 s)', 50,
                                     EasyDAItemChangedEventHandler(itemChangedCallback))

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

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

print('Waiting for 2 seconds...')
time.sleep(2)

print('Finished.')

.NET

Python

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