Maybe I've missed it, but just by looking at the documentation I don't see how I would know to format the extensions. I'm assuming they should be comma separated. I.e.
[FileExtensions(Extensions = ".pdf,.doc,.docx")]
Document Details
⚠ Do not edit this section. It is required for docs.microsoft.com ➟ GitHub issue linking.
ID: 32ba200f-edc6-84ca-4784-5cfd24b6f2ba
Version Independent ID: 0358b515-a6b1-02e8-37c7-9caaba276373
Maybe I've missed it, but just by looking at the documentation I don't see how I would know to format the extensions. I'm assuming they should be comma separated. I.e.
[FileExtensions(Extensions = ".pdf,.doc,.docx")]
Document Details
⚠ Do not edit this section. It is required for docs.microsoft.com ➟ GitHub issue linking.