Excel DNA ribbon problem with strict policies (from 1.7.0-rc8 to current build)

[Heidrun Anger]

Hello everyone,
I am having a problem with ribbon loading of Excel DNA add-ins from version 1.7.0-rc8 onwards in combination with strict Office policies – but only with older versions of Excel (e.g. Excel 2016/2019/2021).

Background:

• From Excel DNA 1.7.0-rc8 onwards, a DummyAddin was used when loading the ribbon to work around a bug in newer Office versions, according to research (https://github.com/Excel-DNA/ExcelDna/commit/c273a9435d01dc9ffbc004ab2c52bf07914ca7e7).
• My environment has very restrictive policies in place (e.g. requireddsig=1, notpromptunsignedaddin=1, vbawarnings=3, etc.) that block unsigned add-ins and macros. My add-in is signed with a certificate.
• The actual add-in is loaded, but the ribbon does not appear and the error message appears in "ExcelDna.Integration.ExcelCommAddinHelper.LoadComAddIn: ComAddIn [Error] The Ribbon/COM add-in helper required by add-in XX could not be registered." In my analysis, I found that the add-in loads correctly, but the ribbon cannot be loaded and GetCustomUI is not executed. It works perfectly with version 1.7.0-rc7, but not with 1.7.0-rc8 or later. We can see similar behaviour with CustomTaskPanes. Here in particular, however, when working with a list of approved add-ins, CustomTaskPanes are not approved because they are given a friendly name but have a generated GUID.

Observation:
With Microsoft 365 (current build) and the same policies, the add-in and ribbon work without any problems.
With Excel 2016/2019/2021 (older builds), the ribbon is not loaded from 1.7.0-rc8 onwards, presumably because the dummy add-in is blocked by the policies.

Questions:
1.    Is this behaviour known, and is there a workaround for older versions of Excel?
2. Is there a way to bypass the dummy add-in or load the ribbon anyway without loosening the policies?
3.    Are there plans to change this behaviour in future Excel DNA versions, or are there best practices for add-in signing in this context?
4.    Is there a solution to the CustomTaskPanes problem that would allow them to work in more restrictive environments?

The policies are set via group policy and cannot be easily relaxed in corporate environments.
Downgrading to an older version of Excel DNA (before 1.7.0-rc8) solves the problem, but is not an option in the long term.

Thank you for any advice or experience reports!

Best regards,
heidi

[Heidrun Anger]

as reminder there was an issue specific to an office update and a workaround was introdruced in 1.7.0-rc8/9 (https://github.com/Excel-DNA/ExcelDna/issues/642) . But after an update of office again, which reverted some changes and fixed the issue, the workaround was never removed from the code. and it seems this workaround causes for older office versions with strict group policies regarding excel some issues. will there be any steps regarding this issue? 

[Govert van Drimmelen]

Hi Heidi,

Thank you for your post - I read it and am thinking about it.

I agree that having the dummy add-in workaround in place forever is not great, but as you see, it all works in current versions. And it worked in the initial problematic COM-addin-loading versions, which is why I did it. But it sounds like there are bad side effects in various other older Excel versions. As you can imagine, I'm also a bit anxious about fiddling with the registration stuff, given how fluid and fragile that aspect of the interaction with Excel is.

I'm not sure how best to approach it, but I would like to have a current Excel-DNA version that will work in the scenarios you face. Whether removing the dummy add-in is enough would be worth investigating. 

For the CTP story, I know we need to make it possible to fix the Guids and ProgIds in your add-in, similar to how we respect the Guid and ProgIds for ribbon extensions. I've bumped the relevant issue: ProgId/Guid for Custom Task Pane Helper · Issue #373 · Excel-DNA/ExcelDna

Give us a bit of time to consider, but please follow up if you don't see progress or attention after a while.

-Govert

[Heidrun Anger]

Thank you for your reply and for looking into this. I know we're talking about older versions here, but some of them are still widely used.
And thank you for looking into the issue with GUIDs and ProgIDs for CTP.
If there's anything I can test, let me know, I'd be happy to do so. Especially for more restrictive environments.

Thank you for your great work.

Heidi