// This example shows how subscribe to changes of a single item in an OPC XML-DA server and display the value of the item
// with each change, using a callback method specified using lambda expression.
using System;
using System.Threading;
using System.Diagnostics;
using OpcLabs.EasyOpc.DataAccess;
namespace DocExamples.DataAccess.Xml
{
class SubscribeItem
{
public static void CallbackLambdaXml()
{
// Instantiate the client object.
var client = new EasyDAClient();
Console.WriteLine("Subscribing item...");
// The callback is a lambda expression the displays the value
client.SubscribeItem(
"http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx",
"Dynamic/Analog Types/Int",
1000,
(sender, eventArgs) =>
{
Debug.Assert(eventArgs != null);
if (eventArgs.Succeeded)
{
Debug.Assert(eventArgs.Vtq != null);
Console.WriteLine(eventArgs.Vtq.ToString());
}
else
Console.WriteLine($"*** Failure: {eventArgs.ErrorMessageBrief}");
},
state: null);
Console.WriteLine("Processing item changed events for 30 seconds...");
Thread.Sleep(30 * 1000);
Console.WriteLine("Unsubscribing items...");
client.UnsubscribeAllItems();
Console.WriteLine("Waiting for 2 seconds...");
Thread.Sleep(2 * 1000);
Console.WriteLine("Finished.");
}
}
}
# This example shows how subscribe to changes of a single item in an OPC XML-DA server and display the value of the item
# with each change, using a 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 import *
from OpcLabs.EasyOpc.DataAccess import *
from OpcLabs.EasyOpc.DataAccess.OperationModel import *
# Item changed callback
def itemChanged(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...')
IEasyDAClientExtension.SubscribeItem(client,
ServerDescriptor('http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx'),
DAItemDescriptor('Dynamic/Analog Types/Int'),
DAGroupParameters(1000),
EasyDAItemChangedEventHandler(itemChanged),
None)
print('Processing item changed events for 30 seconds...')
time.sleep(30)
print('Unsubscribing item changes...')
client.UnsubscribeAllItems()
print('Finished.')
' This example shows how subscribe to changes of a single item in an OPC XML-DA server and display the value of the item
' with each change, using a callback method specified using lambda expression.
Imports OpcLabs.EasyOpc.DataAccess
Namespace DataAccess.Xml
Partial Friend Class SubscribeItem
Shared Sub CallbackLambdaXml()
' Instantiate the client object
Dim client = New EasyDAClient()
Console.WriteLine("Subscribing...")
' The callback is a lambda expression the displays the value
client.SubscribeItem(
"http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx",
"Dynamic/Analog Types/Int",
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,
state:=Nothing)
Console.WriteLine("Processing item changed events for 30 seconds...")
Threading.Thread.Sleep(30 * 1000)
Console.WriteLine("Unsubscribing...")
client.UnsubscribeAllItems()
Console.WriteLine("Waiting for 2 seconds...")
Threading.Thread.Sleep(2 * 1000)
End Sub
End Class
End Namespace
