Modal popup extender

[ingant]

OK ho risolto.
Non importa se aggiungendo l'extender il pannello non si vede, dato che lo posso far comparire utilizzando il metodo show()
dell'extender Modal.
Il codice che mi funziona è il seguente:

 <asp:UpdatePanel ID="UpdatePanel2" runat="server" UpdateMode="Conditional">
                   <ContentTemplate>       
                           <asp:Panel ID="Panel2" runat="server"  Width="150px" Height="268px"  Visible="true">                       
                        <asp:Panel ID="Panel1" runat="server"  Width="150px" Height="268px"  Visible="true"
                            BackColor="#999999" BorderColor="Black" BorderStyle="Ridge" BorderWidth="3px">
                            <asp:Button ID="cmdChiudi" runat="server" Text="Chiudi" 
                                onclick="cmdChiudi_Click" />
                                <br />
                                <br />
                            <asp:GridView ID="GridView3" AutoGenerateColumns="False" runat="server" 
                                CellPadding="4" ForeColor="Black" BackColor="#CCCCCC" 
                                BorderColor="#999999" BorderStyle="Solid" BorderWidth="3px" CellSpacing="2">
                                <Columns>
                                    <asp:BoundField DataField="alias" HeaderText="Misura" />
                                    <asp:BoundField DataField="valore" HeaderText="Valore" />
                                </Columns>
                                <FooterStyle BackColor="#CCCCCC" />
                                <HeaderStyle BackColor="Black" Font-Bold="True" ForeColor="White" />
                                <PagerStyle BackColor="#CCCCCC" ForeColor="Black" HorizontalAlign="Left" />
                                <RowStyle BackColor="White" />
                                <SelectedRowStyle BackColor="#000099" Font-Bold="True" ForeColor="White" />
                                <SortedAscendingCellStyle BackColor="#F1F1F1" />
                                <SortedAscendingHeaderStyle BackColor="#808080" />
                                <SortedDescendingCellStyle BackColor="#CAC9C9" />
                                <SortedDescendingHeaderStyle BackColor="#383838" />
                            </asp:GridView>
                        </asp:Panel>   
                        </asp:Panel>                                   
                        <ajaxToolkit:DragPanelExtender ID="Panel1_DragPanelExtender" runat="server" 
                           BehaviorID="Panel1_DragPanelExtender" DragHandleID="Panel1"  
                           TargetControlID="Panel1" />
                        <ajaxToolkit:ModalPopupExtender ID="Panel1_ModalPopupExtender"  PopupControlID="Panel1"    CancelControlID="Panel1"
                        runat="server" BehaviorID="Panel1_ModalPopupExtender" DynamicServicePath=""  Enabled="true"
                      TargetControlID="Panel1">
                        </ajaxToolkit:ModalPopupExtender>                                             
                    </ContentTemplate>
                    </asp:UpdatePanel>