I'm afraid you can not refresh gridview in that manner. You have to use javascript function to bind gridview again after uploading in ajax file upload.
You can do one of the following:
1) simply use OnClientUploadComplete="ShowUpdate()" in ajax file upload control and use
<script type="text/javascript">
function ShowUpdate() {
__doPostBack();
}
</script>
as its javascript function.
2) you can put the gridview inside update panel and then postback the update panel using javascript function OnClientUploadComplete of ajax file upload
You may refer below links to get your job done:
AjaxFileUpload+to+refresh+GridView+after+upload+complete[
^]
reload-gridview-or-repeater-on-ajaxfileupload-uploadcomplete-event-in-asp-net[
^]
Hope it Helps.. Happy Coding! :)