// This example shows how subscribe to changes of a single item and display the value of the item with each change,
// using a callback method specified using lambda expression.
using System;
using System.Diagnostics;
using System.Threading;
using OpcLabs.EasyOpc.DataAccess;
namespace DocExamples.DataAccess._EasyDAClient
{
partial class SubscribeItem
{
public static void CallbackLambda()
{
// Instantiate the client object.
var client = new EasyDAClient();
Console.WriteLine("Subscribing...");
// The callback is a lambda expression the displays the value
client.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Random", 1000,
(sender, eventArgs) =>
{
Debug.Assert(eventArgs != null);
if (eventArgs.Succeeded)
{
Debug.Assert(eventArgs.Vtq != null);
Console.WriteLine(eventArgs.Vtq.ToString());
}
else
Console.WriteLine("*** Failure: {0}", eventArgs.ErrorMessageBrief);
});
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 and display the value of the item with each change,
# using a regular callback method.
# 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='')
# Instantiate the client object.
client = EasyDAClient()
print('Subscribing item changes...')
# The callback is a regular method that displays the value.
IEasyDAClientExtension.SubscribeItem(client,
'', 'OPCLabs.KitServer.2', 'Simulation.Random', 1000,
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.')
' This example shows how subscribe to changes of a single item and display the value of the item with each change,
' using a callback method specified using lambda expression.
Imports OpcLabs.EasyOpc.DataAccess
Namespace DataAccess._EasyDAClient
Partial Friend Class SubscribeItem
Shared Sub CallbackLambda()
' Instantiate the client object
Dim client = New EasyDAClient()
Console.WriteLine("Subscribing...")
' The callback is a lambda expression the displays the value
client.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Random", 1000,
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)
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
