If you want to call ReadMultipleItems periodically, you will need to write that code, based on timer event or so.
DAVtqResult does not contain ItemID, but it is the same ItemID as passed into the method in the element of an array with the same index as the result. That should normally be sufficient, as you can refer back to the input array, and take the ItemID from the corresponding element there. Some people do not like it that way, and want additional information (such as ItemID) "go through", appear in the results. If you require this, you can use the ReadMultipleItems overload that takes an input array of DAItemArguments objects, and each DAItemArguments has a State property which is an Object and you put there any data you like - e.g. an ItemID, or even a reference back to the same DAItemArguments object. The State is then available in each DAVtqResult after ReadMultipleItems method returns.

Hello.
Could it be the reason that many items actually do not change their values? (With some simplification, ) OPC Servers are required to send notifications only if the value or the quality have changed.

<span style="font-family: "Calibri","sans-serif"; color: #1f497d; font-size: 11pt; mso-ascii-theme-font: minor-latin; mso-hansi-theme-font: minor-latin; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: minor-bidi; mso-themecolor: dark2">Hello,
<span style="font-family: "Calibri","sans-serif"; color: #1f497d; font-size: 11pt; mso-ascii-theme-font: minor-latin; mso-hansi-theme-font: minor-latin; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: minor-bidi; mso-themecolor: dark2">
<span style="font-family: "Calibri","sans-serif"; color: #1f497d; font-size: 11pt; mso-ascii-theme-font: minor-latin; mso-hansi-theme-font: minor-latin; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: minor-bidi; mso-themecolor: dark2">For most usages, it is easier and fine to just use the ItemChanged event. You can freely use it even if you subscribe using SubscribeMultipleItems.

<span style="font-family: "Calibri","sans-serif"; color: #1f497d; font-size: 11pt; mso-ascii-theme-font: minor-latin; mso-hansi-theme-font: minor-latin; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: minor-bidi; mso-themecolor: dark2">Every item change gets notified using BOTH ItemChanged and MultipleItemsChanged events. So you really just need to pick one which is better, but never use both together. If there are multiple changes arriving "together" from the OPC Server, it is slightly more efficient to hook to MultipleItemsChanged, because there is just one notification, and not say 100 notifications. Inside that handler, you then need to loop through the ArgsArray provided, and then process each object in the same way as you would do in ItemChanged event handler.

<span style="font-family: "Calibri","sans-serif"; color: #1f497d; font-size: 11pt; mso-ascii-theme-font: minor-latin; mso-hansi-theme-font: minor-latin; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: minor-bidi; mso-themecolor: dark2">However, the performance difference is quite small in QuickOPC.NET (the event exists mainly for symmetry with QuickOPC-COM, where the EAsyDAClient object usually runs in a separate process, and method calls and event notifications are much costlier).

<span style="font-family: "Calibri","sans-serif"; color: #1f497d; font-size: 11pt; mso-ascii-theme-font: minor-latin; mso-hansi-theme-font: minor-latin; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: minor-bidi; mso-themecolor: dark2">An example for MultipleItemsChanged is in the Reference documentation for that event. It looks like this:

<span style="font-family: "Calibri","sans-serif"; color: #1f497d; font-size: 11pt; mso-ascii-theme-font: minor-latin; mso-hansi-theme-font: minor-latin; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: minor-bidi; mso-themecolor: dark2">
// This example shows how to process multiple item changes in one callback.

using OpcLabs.EasyOpc.DataAccess;
using System;
using System.Threading;

namespace DocExamples
{
namespace _EasyDAClient
{

class MultipleItemsChanged
{
public static void Main()
{
using (var easyDAClient = new EasyDAClient())
{
easyDAClient.MultipleItemsChanged += easyDAClient_MultipleItemsChanged;

easyDAClient.SubscribeMultipleItems(
new[] {
new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, null),
new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Ramp (1 min)", 1000, null),
new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Sine (1 min)", 1000, null),
new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Register_I4", 1000, null)
});

Console.WriteLine("Processing multiple item changed events for 1 minute...");
Thread.Sleep(60 * 1000);
}
}

// Multiple items changed event handler
static void easyDAClient_MultipleItemsChanged(object sender, EasyDAMultipleItemsChangedEventArgs es)
{
Console.WriteLine();
EasyDAItemChangedEventArgs[] a = es.ArgsArray;
foreach (EasyDAItemChangedEventArgs e in a)
Console.WriteLine("{0}: {1}", e.ItemDescriptor.ItemId, e.Vtq);
}
}
}


Best regards