As it’s complicated to maintain the AjaxFileUpload selected file on change of DropdownList we added Update panel to all the control which need to be maintain the state as per the action fire. But for AjaxFileUpload if we change UpdateMode to always it will work only if file not selected before the dropdownchange or if we selected file before dropdown change. So in this case maintain the selected file is bit complicated as AjaxFileUpload get disabled on other event which fires from different control which placed in update panel. But if you note it just Disable the AjaxFileUpload on change of Dropdown so we can do one trick by using jQuery by enabling the AjaxFileUpload on Mouseover so user can able to select the Files every time.
Refer the below script and try it at your end as per your logic.
jQuery
<head id="Head1" runat="server">
<title></title>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>
<script type="text/javascript">
$(function () {
$("[id*=AjaxFileUpload11]").mouseover(function () {
$("[id*=AjaxFileUpload11]").removeAttr("disabled");
});
});
</script>
</head>
Screenshot
