<ajax:UpdatePanel ID="UpdatePanelCarrello" runat="server" EnableViewState=true UpdateMode ="Conditional">
                            <ContentTemplate>  
                             
                            <asp:Panel runat ="server"  ID="PanelCarrello" Visible= "true" EnableViewState ="true" >
                            

....
....

<tr>
                                                                      
                                    <td width="100%" valign="middle" align="left" class="TableBase">
                                    <br />
                                    <Font class="TestiVerdiBIG"><%=Resources.ResourceCatalogo.lblScontoSpeciale%></Font>
                                    <asp:Label ID="lblApplicaSconto" runat ="server" CssClass ="TestiRossiMedi" Text ="" />
                                    <asp:TextBox runat ="server" ID="txtSconto" CssClass ="TextBoxCenterEvidenza" Text =""></asp:TextBox>
                                    <asp:RequiredFieldValidator ID="RequiredFieldValidatorTxtSconto" ControlToValidate ="txtSconto" runat="server" CssClass="TestiRossi" ErrorMessage="<%$Resources:ResourceMsg, CampoVuoto %>" Display =Dynamic></asp:RequiredFieldValidator>
                                    <asp:Button runat ="server" ID="btnApplicaSconto" CommandName="DecreasePrice" Text ="<%$Resources:ResourceCatalogo,lblApplicaSconto%>" />
                                    <asp:Label ID="lblScontoApplicato" runat ="server" CssClass ="TestiVerdiBIG" Text ="" />
                                    <br /><br />
                                    </td>
                                    
                                </tr>

...
...

</asp:Panel>
                            
                            </ContentTemplate>
                            </ajax:UpdatePanel>