Hi,
Thank you for your quick answer !
I understand your solution but I tried to call a method of my controller (selecting_multiple_files) but it's never been hit by my breakpoint.
The only thing (and the most important) that I didn't understand is how to call this method instead of OnFileUploaded (because when this method is called, it seems to be too late to get the value of my field).
 
I tried to change the method called in the form:
@{Html.BeginForm("selecting_multiple_files","trackerController");}
@Html.Raw(ViewBag.uploaderhtml)
@{Html.EndForm();}
 
or is it possible to overwrite OnFileUploaded to put the field value with Javascript?

Thank you,

FlorentG