How to Use upload a image in Gridview when on update button

GridView On the Page

<asp:TemplateField HeaderText="File Attachment" sortExpression="strFileAttachment">
                <ItemTemplate>
                    <p>
                        <%#Eval("strFileAttachment")%>
                    </p>
                </ItemTemplate>

                <EditItemTemplate>
                    <asp:FileUpload ID="FileUploadFileAttachment"     runat="server" />                    
                </EditItemTemplate>

</asp:TemplateField>

protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)

{

FileUpload FileUpload1 = (FileUpload)GridView1.Rows[e.RowIndex].FindControl("FileUploadFileAttachment");

}

I think this may solve your problem.
Let me Know if it will work for you.