No, Delphi is not .NET based, Delphi is COM based, therefore it uses QuickOPC-COM.

I have written that you cannot use callbacks in QuickOPC-COM, and therefore Delphi (maybe I have not made this clear enough).

Or are you now talking about a different tool, not Delphi?

Hello.

Ad 1) Yes. Example comes with the product, under ExamplesCom\OP\DelphiXE7\UADocExamples, there are several examples - for UABrowseDialog, UADataDialog, UAEndpointDialog, UAHostAndEndpointDialog.

Ad 2) In QuickOPC.NET you can use callbacks instead of events, and specify a different callback function with each SubscribeDataChange.

QuickOPC-COM only has events, no callbacks, therefore this is not possible - that's how events work. You need to use the State (any value provided by your code, not the Handle) to distinguish between different subscriptions.

In theory you could create multiple EasyUAClient objects and then hook a different event handler on each of them. That will work, and on the server side it would even be efficient, because all EasyUAClient objects are handled by the same underlying engine, but it will be inefficient on the client side, causing extra resources be consumed with each EasyUAClient. If you have just a handful of items, or groups of items, then you can do that. But do not create hundreds or more EasyUAClient objects - that would not be a good idea.

Regards