Using FileUpload Control inside ASP.Net AJAX UpdatePanel Control

I have tried below both coding part.   My requirement is to add images to griedview lines. So when I am clicking on an item in grid, it will popup a div   containing fileuplod control. 

I need to update this without refreshing page.  so when I am using  <asp:AsyncPostBackTrigger ControlID="Btn_UploadImage" EventName="Click" />  I am not getting  "hasfile" or file name.  

but if I use second option -- <asp:PostBackTrigger ControlID="Btn_UploadImage" />  working properly,   BUT PAGE REFRESHING / POSTBACK IS WORKING.   I need to do this without refreshing the page. 

<Triggers> <asp:AsyncPostBackTrigger ControlID="Btn_UploadImage" EventName="Click" />  </Triggers>

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<Triggers> <asp:PostBackTrigger ControlID="Btn_UploadImage" /> </Triggers>

regards,

Sajeesh