Additional note: If you subscribe to the same item two or more times, only the lowest percent deadband will be used. Similarly, if you subscribe to the same item with different update rates, only the fastest update rate will be used. This behavior is by design.

Hello, I have attempted to reproduce with recent QuickOPC.NET, and our simulation server, and it works correctly for me. I admit, however, that I have falled into a trap of using a wrong overload of SubscribeItem method - it is easy to code it so that what one thinks is the percent deadband is actually a 'state' argument. Below is the code that works for me - with the "problematic" line highlighted in yellow.


        partial class ChangeItemSubscription
        {
            public static void PercentDeadband()
            {
                using (var easyDAClient = new EasyDAClient())
                {
                    var eventHandler = new EventHandler<EasyDAItemChangedEventArgs>(easyDAClient_ItemChanged_PercentDeadband);
                    easyDAClient.ItemChanged += eventHandler;
 
                    Console.WriteLine("Subscribing with 10% deadband...");
                    int handle = easyDAClient.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Ramp 0-100 (10 s)", 
                        VarType.Empty, 100, 10.0f, null);
 
                    Console.WriteLine("Waiting for 10 seconds...");
                    Thread.Sleep(10 * 1000);
 
                    Console.WriteLine("Changing subscription to 0% deadband...");
                    easyDAClient.ChangeItemSubscription(handle, new DAGroupParameters(100, 0.0f));
 
                    Console.WriteLine("Waiting for 10 seconds...");
                    Thread.Sleep(10 * 1000);
 
                    Console.WriteLine("Unsubscribing...");
                    easyDAClient.UnsubscribeAllItems();
 
                    Console.WriteLine("Waiting for 10 seconds...");
                    Thread.Sleep(10 * 1000);
                }
            }
 
            // Item changed event handler
            static void easyDAClient_ItemChanged_PercentDeadband(object sender, EasyDAItemChangedEventArgs e)
            {
                Console.WriteLine(e.Vtq);
            }
        }

If you do not find a solution in the above code, can you please send me relevant parts of your program so that I can look at it?
Thank you
Zbynek Zahradnik

OK I will set it up here and attempt to reproduce. I will let you know about the outcome when it is ready.

Can you try with latest QuickOPC from our Web site?

Hello,
I do not quite understand the nature of your problem. Can you please describe in more details?
Re "easyDAClient1_ItemChanged" return results at every "requestedUpdateRate". : Not sure what this means. The ItemChanged notifications should be called roughly in a rate given by the requestedUpdateRate (or slower, if there are no changes). Are you saying that this is not happening?
Re "Parameter "deadband" is not to take into.": Do you mean that it appears that this parameters is ignored? if so, can you please tell us: 1) Which OPC server are you connecting to, and 2) What type is the data item you are conecting to? (only items with "Analog" kind are subject to deadband filtering; other kinds of items DO ignore the deadband, this is per OPC specification, and 3) what is the precise version and build number of QuickOPC you are using? (there might have been builds with a bug with that effect; but the recent release should work well).
Best regards,
Zbynek Zahradnik