OK, although it is recorded in the forum thread log that you confirmed that the other application is OPC Classic client, I will now work under the premise that it is actually an OPC UA client.

We already had a long discussion about OPC UA NodeIds some time ago on this forum. I do not want to repeat the long parts of it. What I will do is that I simply offer you what to do.

Option 1. Simply remove the "nsu=" part the way I described. The problem with this approach is that it does not pass the namespace URIs from one application to the other, it only passes namespaces indexes. And the namespaces indexes can, at least with some servers, change as the server is reconfigured, or even between sessions. Most people are not aware of this problem and also things work most of the time, but you should be aware of it.

Option 2. The proper way of doing things would be to pass the namespace URI (the "nsu=") part to your other application, and actually ignore the namespace index. And find a way, inside that other application, to specify nodes using the namespace URI and not the namespace index. I do not how the other application is constructed or whether this is doable at all. It's not my task, but that would be the fully correct way of doing it.

Regards

No. I have not misunderstood. I have asked you "...And you pass them to other application, which is using OPC Classic. ", to which you replied "Yes, Correct".
So we are back where we were before. I do not understand what you are doing, because you are changing your answers in fundamental ways.

Which of the statements is correct then?

And, if the external process is using OPC UA, how comes that it returns an error that is very much like OPC Classic error code (C0040008 )? And, you have not provided that full error message/screenshot to me yet, although I have asked for it.

Regards

I do not see why you are doing it this way. If you want to use the item Ids via OPC Classic (the external process) , then why you don't you also obtain them via OPC Classic browsing in your app? That way they will always be correct.

There is no standard, required mapping between OPC Classic item Ids and OPC UA Node Ids. Things that work with some or many servers are not guaranteed to work with others. If you want to write a software that is for generic use, this is not the way to go.

If you are fine with limiting yourself to server/server that do the mapping in a specific way, then of course you might do it.

Which bring me finally to the answer to the question you asked. In order to get the node Id without the "nsu=" part, do this:

1. From an existing UANodeId (e.g. the .NodeId property in UANodeDescriptor), make a copy, using a copy constructor. In C# that would something like "UANodeId nodeIdWithoutnamespaceUri = new NodeId(myExistingNodeId)";
2.Set the .NamespaceUriString property of this copy to an empty string. In C#, that would be something like "nodeIdWithoutnamespaceUri.NamespaceUriString = "";".
3. You can now take nodeIdWithoutnamespaceUri.ExpandedText and the string you are looking for will be there.

Regards

Hello, we are getting there.

Is this correct understanding:

- You have obtained some node Ids over OPC UA, using your app with QuickOPC/
- And you pass them to other application, which is using OPC Classic. And they do not work, giving error C0040008 .

And you expect them to work?

I still do not understand. Where you have posted is not important.
Error C0040008 related to OPC DA only. Post here the full error message, screen snapshot, or whatever helps me understand. You cannot mix Classic and UA node/item ids.

Does your server support both OPC UA and OPC Classic? Or are you using some kind of wrapper/convertor?

Without understanding what you are trying to achieve, I cannot answer the question, because it makes no sense to me.

Regards