The SubscribeMultipleDataChanges method is available since QuickOPC 2021.3: kb.opclabs.com/What%27s_new_in_QuickOPC_2021.3#OPC_UA_Client-Server .

Either upgrade QuickOPC, or use the approach from the code I provided to achieve the same.

Best regards

OPC Labs QuickOPC 2020.3

Hello.

Which QuickOPC version are you using?

Regards

The SubscribeMultipleDataChanges extension method seems to be documented on the link you sent, but it doesn't recognize it in my program. Below is the error I receive with the directives I am using. Can you provide an example for passing a DataChangeCallback in the EasyUAMonitoredArguments.

using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.OperationModel;

"Error CS1061 'EasyUAClient' does not contain a definition for 'SubscribeMultipleDataChanges' and no accessible extension method 'SubscribeMultipleDataChanges' accepting a first argument of type 'EasyUAClient' could be found (are you missing a using directive or an assembly reference?)

Hello.

you are probably looking for the SubscribeMultipleDataChanges extension method: opclabs.doc-that.com/files/onlinedocs/QuickOpc/Latest/User's...scribeMultipleDataChanges.html .

The other way to do this is to use the DataChangeCallback property ( opclabs.doc-that.com/files/onlinedocs/QuickOpc/Latest/User's...uments~DataChangeCallback.html ) in each of the the EasyUAMonitoredArguments passed to the SubscribeMultipleMonitoredItems method.

This is what, internally, the SubscribeMultipleDataChanges does anyway. Its implementation (the code is simplified) looks like this:

static public int[] SubscribeMultipleDataChanges(

this IEasyUAClient client,

UAMonitoredItemArguments[] monitoredItemArgumentsArray,

EasyUADataChangeNotificationEventHandler dataChangeCallback)

{

return client.SubscribeMultipleMonitoredItems(monitoredItemArgumentsArray

.Select(arguments => new EasyUAMonitoredItemArguments(dataChangeCallback, arguments)).ToArray());

}

Best regards/S pozdravem

I am switching from OPC DA to OPC UA. In OPC DA the SubscribeMultipleItems method comes with a callback argument. For OPC UA the SubscribeMultipleMonitoredItems method does not come with a callback argument. How can I implement a callback for SubscribeMultipleMonitoredItems in OPC UA?

OPC DA Example:

easyDAClient1.SubscribeMultipleItems(items.ToArray(), (_, e) => {

if (e.Vtq != null && e.Vtq.HasValue)

{

String tag = e.Arguments.ItemDescriptor.ItemId.ToString();

object value = e.Vtq.Value;

itemChanged(tag, value);

}

});

OPC UA Example:

easyUAClient1.SubscribeMultipleMonitoredItems(items.ToArray());