I want to show a command extension on a commanBar Picture library but it is not giving results.
I understeand that i must configure the element.xml file ,RegistrationId and RegistrationType fields, but i can't find the way to make it work.
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Can you share your elements.xml file with us?
Title="MyExtension
RegistrationId="109"
RegistrationType="List"
Location="ClientSideExtension.ListViewCommandSet.CommandBar"
Can you provide a bit more information for us? SharePoint version/SPFx version and your deployment process?
I use spfx v1.7.0.
gulp bundle --shipgulp package-solution --shipand then i upload the file to my AppCatalog
So I assume this means SharePoint Online. And are you using tenant wide deployment or manually adding the apps to your site?
I'm adding manually the apps to my site
Have you tried upgrading the project to the latest version of SPFx (v1.9.1) to see if there is any change?
When I test this in my environment(SPFx 1.8.2), I found the RegistrationId revert to default 100 in SPFx package, check the image below.

This cause extension doesn't apply to Picture library.
So I use 7-zip to edit the RegistrationId to 109 and redeploy the solution to tenant(uninstall the solution from target site, remove from recycle bin), re-add the app to target site, and it works now.

When you shared the elements.xml file above, that's the one in the ./sharepoint/assets, correct?
You're saying when you built the project, the build process changed the registration ID?
Yes the above solution worked for me too. I did the same for the Site pages with Registration Id to 119.
Uninstall and Reinstall is also a crucial step. And dont forget to change the version of the app.
@andrewconnell the RegistrationId of elements.xml in /sharepoint/assets is set to 109, when package the solution, the RegistrationId of elements.xml in package(.sppkg) and /sharepoint/solution/debug/featureid both set to 100.
@OS-Lee / @Carolinavv
Do you have a repro solution (link to public GH repo) you can share that shows this?
After I update ListTemplateId(ListTemplateId="109") of ClientSideInstance.xml to keep the same as elements.xml(RegistrationId="109") and package, the RegistrationId="109" set to correct value now.
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