modalpopupextender is popup in both condition

I am trying to implement  modalpopupextender but now problem is that panel is visible in both condition. but my target is that when modalpopupextender  visible when condition true. I am trying in this way.

       protected void btn_mark_favorite_Click(object sender, EventArgs e)
        {
            try
            {
                if (UserID != 0)
                {

                    ModalPopupExtender2.Show();
                    Panel1.Visible = false;

                }
                else
                {
                    Response.Redirect("Home.aspx");
                    ModalPopupExtender2.Show();
                }
            }
            catch (Exception ex)
            { }
        }

<asp:ModalPopupExtender ID="ModalPopupExtender2" TargetControlID="btn_mark_favorite" runat="server" PopupControlID="Panel1" BackgroundCssClass="modalBackground"  CancelControlID="btn_cancle_2"></asp:ModalPopupExtender><asp:Panel ID="Panel1" runat="server" CssClass="modalPopup" align="center" style = "display:none"><br /><p>Login first then try to favorite!</p><asp:Button ID="btn_cancle_2" runat="server" Text="Cancle"  BackColor="#0066ff" ForeColor="White" Font-Bold="true" Font-Names="Tahoma" Height="25" Width="70" BorderStyle="None" OnClick="btn_cancle_2_Click"   /></asp:Panel>