// 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.Diagnostics;
using OpcLabs.EasyOpc.DataAccess;
using System;
using System.Threading;
 
namespace DocExamples
{
    namespace _EasyDAClient
    {
        partial class SubscribeItem
        {
            public static void CallbackLambdaXml()
            {
                // Instantiate the client object
                var 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,
                    (sender, eventArgs) =>
                        {
                            Debug.Assert(eventArgs != null);
 
                            if (eventArgs.Exception != null)
                                Console.WriteLine(eventArgs.Exception.ToString());
                            else
                            {
                                Debug.Assert(eventArgs.Vtq != null);
                                Console.WriteLine(eventArgs.Vtq.ToString());
                            }
                        },
                    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);
            }
        }
    }
}