<asp:Panel ID="Panel1" runat="server" visible='<%# HttpContext.Current.User.Identity.IsAuthenticated %>'>
<a dir="rtl" target="_self" href='Show/Dawnload.aspx?Atach=<%#Eval("Atach")%>'>
<img src="AfDanload_files/1157.png" title="دانلود فایل : <%#Eval("Subject")%>" />
</a>
</asp:Panel>



if (this.Page.User.Identity.IsAuthenticated)
{
Panel1.Visible = true;
}
else
{
Panel1.Visible = false;
}