upload only after another ajax .net

I have a page with a long form of fields. i validate it via JS and send it with AJAX. once it is in the DB and i have a index id from the DB i want to upload the files and attach them to the right form in the db

i have the main form of the .NET so i can't have another form, and in addition i want it to be able to upload the files to the view, just like the demo they have on their website enter link description here

is there any way to do that?