Dropbox API: find the the members of single shared file

It's currently not possible to get the members of a single shared file, but I'll be sure to pass this along as a feature request.

To your current solution: I don't think this will work. Single-shared-file members are not necessarily the same as shared folder members. You can call /list_folder (to get the contents of a folder) or /get_metadata and pass in include_has_explicity_shared_members=true, and any FileMetadata returned will tell you whether or not a file has explicit shared members in the has_explicit_shared_members field; however, it won't give you information about the actual users.