Unable to load Plug-in: ID already in use. Rhino 6SR31


Some of our users are experiencing some issues with the plug-in we develop when they upgraded to SR30 and SR31.
Specifically we have encountered 2 issues, which I am not sure if they are related.

Issue one (happening, as far as we know, since SR30):
The reference to the document in the event arguments of EndOpenDocument is sometimes null when a new document (not previously saved) is opened. I have only been able to catch this once when using any of the 2 machines where I develop the plug-in, regardless of whether I start it from the development environment or just from Rhino’s executable directly.
This however seems to happen consistently with other machines.
This never seems to happen if I open a previously saved document.

I am not sure if this is expected behavior, a bug or a problem with my implementation. Any pointers?

Issue two (confirmed to happen only with SR31):
Since SR31 our plug-in won’t load, with Rhino showing the following message:

Unable to load Plug-in: ID already in use

I have checked in the registry for other plug-ins with the same ID, and I have also tried uninstalling any previously installed version and reinstalling, as well as removing the registry entry, but nothing seems to help.

Interestingly, the first time Rhino is opened after installing the plug-in, everything goes smoothly. But the next time is when the message pops. If Rhino is started in safe mode, and the plug-in is loaded manually everything runs smoothly too. So my guess is that there is a conflict with some other plug-in, but I can’t find any.

In the machine where I develop the plug-in this does not happen either, but it does with any other machine, even with new installations of Rhino.

Any pointers as to what can the source be or how can I troubleshoot it?

I am not too worried about about Issue 1 because it is a fringe case and there is a workaround, however Issue 2 is giving me some headaches, and I have had to ask some of our users to downgrade to SR30.

Thanks in advance.

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Hi @endika,

If we were to have your plug-in installer, can you provide us step-by-step instructions on how to repeat what you are seeing?


– Dale

Hi Dale,

Of course. What is the best way for me to share it with you?

Sent a private message!

I have the same issue, is this solved?

In the case above, the .rhi included both two copies of the plug-in assembly, one with a .rhp extension and one with the original .dll extension. Removing the .dll solved the issue. This was for a RhinoCommon (.NET) plug-in.

1 Like