I am trying to create a custom control for updating a List on a Sharepoint site that only allows Sandbox Solutions to be added.
I've read a few threads on uploading attachments, but they all seem to involve doing it from the server machine (Using a file stream to read a local file).
Is it not possible to use Javascript or something to pass a file through to a Sandbox'd webpart??
The answer, it seems, is no. You cannot.