<asp:scriptmanager id="ScriptManager1" runat="server" xmlns:asp="#unknown">
</asp:scriptmanager>
<asp:updatepanel xmlns:asp="#unknown">
ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
<contenttemplate>
</contenttemplate>
<asp:asyncpostbacktrigger controlid="btnUpload" eventname="Click" />
</asp:updatepanel>
in code behind:
on button click event
GridView1.DataBind();
UpdatePanel1.Update();