DocSpace

ONLYOFFICE DocSpace is a room-based collaborative platform which allows organizing a clear file structure depending on users' needs or project goals. Flexible access permissions and user roles allow fine-tuning the access to the whole space or separate rooms. Maintained by ONLYOFFICE on GitHub, where it has earned 265 stars from the community.

It's actively developed around collaboration, dotnet, file-sharing, and is a solid reference for anyone building with these tools.