atlas无刷新录入界面，不能选择日期？

atlas无刷新录入界面，不能选择日期？
在文本框中，单击弹出日期选择控件，选择后文本框中没有返回选择的日期值，如果录入界面不是无刷新界面则没有问题。
<form id="form1" runat="server">
    <atlas:ScriptManager ID="ScriptManager1" EnablePartialRendering="true" runat="Server" />
    <div>
             <atlas:UpdatePanel ID="up1" runat="server">
              <ContentTemplate>
        <table id="query" style="font: caption ;width: 305px" border="0" cellpadding="3" cellspacing="0">    
            <tr>
                <td style="width: 10px; height: 12px " align="right">
                    <asp:CheckBox ID="cb7" runat="server" Width="50px" TextAlign="Left" /></td>
                <td style="width: 68px; height: 12px" align="right">操作时间:</td>
                <td style="width: 101px; height: 12px">
                     <asp:TextBox ID="txtDate" runat="server" Width="161px"></asp:TextBox>
                </td>
            </tr>
        </table>
         <atlasToolkit:PopupControlExtender ID="PopupControlExtender1" runat="server">
        <atlasToolkit:PopupControlProperties TargetControlID="txtDate" PopupControlID="Panel1" Position="Bottom" />  
    </atlasToolkit:PopupControlExtender>
   </ContentTemplate>
     </atlas:UpdatePanel>
     <asp:Panel ID="Panel1" runat="server" CssClass="popupControl">
        <atlas:UpdatePanel ID="UpdatePanel2" runat="server">
            <ContentTemplate>
               <center>
                     <asp:Calendar ID="Calendar1" runat="server" BackColor="White" BorderColor="#999999" CellPadding="1" DayNameFormat="Shortest" Font-Names="Verdana" Font-Size="8pt" ForeColor="Black" Width="160px" OnSelectionChanged="Calendar1_SelectionChanged">
                        <SelectedDayStyle BackColor="#666666" Font-Bold="True" ForeColor="White" />
                        <TodayDayStyle BackColor="#CCCCCC" ForeColor="Black" />
                        <SelectorStyle BackColor="#CCCCCC" />
                        <WeekendDayStyle BackColor="#FFFFCC" />
                        <OtherMonthDayStyle ForeColor="#808080" />
                        <NextPrevStyle VerticalAlign="Bottom" />
                        <DayHeaderStyle BackColor="#CCCCCC" Font-Bold="True" Font-Size="7pt" />
                        <TitleStyle BackColor="#999999" BorderColor="Black" Font-Bold="True" />
                    </asp:Calendar>
                </center>
            </ContentTemplate>
        </atlas:UpdatePanel>
    </asp:Panel> 
    </div> 
    </form>

using AtlasControlToolkit;

public partial class Samples_template_testTime : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
   
    protected void Calendar1_SelectionChanged(object sender, EventArgs e)
    {
        PopupControlExtender.GetCurrent(this.Page).Commit(Calendar1.SelectedDate.ToShortDateString());
    }
}