Check if the upload is required.
Set the upload as (not) required. @NOTE: Only for web purposes, server side is unaffected!
set to required (true)or not required (false)
Check if the field content is valid:
Disable the file upload.
Enable the file upload.
Get the number of files (uploaded & selected for upload).
Get the number of selected but not uploaded files.
Get the number of already uploaded files.
Get the value of the control. At the moment the filename(s) will be returned.
Check if the upload is enabled.
Check if the upload is required.