FileUpload Control inside ASP.Net AJAX UpdatePanel Control

Hi,

    I use FileUpload Control to upload image and save data inside ASP.Net AJAX UpdatePanel Control.
The following is my code-It work fine.
<asp:PostBackTrigger ControlID="SaveButton" />

  But after I save the data successful,I refresh the web form and it save the same data again.
  So how do I avoid the error? Thanks.