Hi Felix,

I'm afraid this won't be possible without actually reading the files from the filesystem, the only things the AttachmentsHelper provide is a method to get all filenames from the attachments from a DOM Instance, and a method to get the file contents as a byte array.

The best approach would probably be to read out the files yourself from the documents folder to get that info.
Note that we are working on a feature that allows you to save DOM attachments to a network share instead of the Documents folder. If that would be configured, the process that runs the data source would need access to that network share.

An alternative, but this is probably also not very ideal, could be to create a DOM definition to manage data about your attachments. You could create a script to create a DOM Instance for every attachment uploaded, containing the info about it you need.

Let me know if I can be of further help!