Hi,
You need understand the steps how the uploader works for MVC
The uploader will make a GUID for each file, and upload it to server at first.
After the file data be uploaded , it's a temp file on server side.
You can get the GUID on client side , and then you can send the GUID and your custom data to the server side via submitting the form.
At server side, you can use the mvcuploader.GetUploadedFile(guid) to get the temp file.
By the way , did you check our samples for the MVC ?
Regards,
Terry