.net页面调试时闪上就丢失，

.net页面调试时闪下就丢失，求助！！急
代码调试时，页面闪下就丢失了，直接上代码；[code=C#][/code]<%@ Page Language="C#" MasterPageFile="~/SampleManager/Sample.Master" AutoEventWireup="true" CodeBehind="CreateSampleOrder.aspx.cs" Inherits="Flag.Net.SampleManager.CreateSampleOrder" Title="Create Sample Order" %>

<%@ Register Assembly="DevExpress.Web.ASPxGridView.v9.3.Export, Version=9.3.4.0, Culture=neutral, PublicKeyToken=b88d1754d700e49a"
  Namespace="DevExpress.Web.ASPxGridView.Export" TagPrefix="dx" %>

<%@ Register Assembly="DevExpress.Web.ASPxGridView.v9.3, Version=9.3.4.0, Culture=neutral, PublicKeyToken=b88d1754d700e49a"
  Namespace="DevExpress.Web.ASPxGridView" TagPrefix="dx" %>
<%@ Register Assembly="DevExpress.Web.ASPxEditors.v9.3, Version=9.3.4.0, Culture=neutral, PublicKeyToken=b88d1754d700e49a"
  Namespace="DevExpress.Web.ASPxEditors" TagPrefix="dx" %>
<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">  
  <asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
  <ContentTemplate>
  <div>
  <table border="0" cellpadding="0" cellspacing="0" style="width: 99%; height: 50px; position: relative; top: 0px;left:5px; z-index: 101;">
  <tr>
  <td style="height:25px; width: 563px;">
  <asp:Button ID="btClear" runat="server" Text="Clear" /><asp:DropDownList ID="drpDType"
  runat="server">
  <asp:ListItem>ImportDate</asp:ListItem>
  <asp:ListItem>ShipDate</asp:ListItem>
  </asp:DropDownList>
  <asp:TextBox ID="txtFrom" runat="server"></asp:TextBox>
  <asp:Label ID="Label1" runat="server" Text="Factory" Width="59px"></asp:Label>&nbsp;
  <asp:TextBox ID="txtFactory" runat="server"></asp:TextBox>
  <br />
  <asp:Button ID="btnMore" runat="server" Text="MoreOption" Width="136px" />
  <asp:Button ID="butQuery" runat="server" Text="Go" Width="51px" OnClick="butQuery_Click" />
  &nbsp;<asp:Button ID="btnCreate" runat="server" Text="Create Order" OnClick="btnCreate_Click" />
  <asp:Button ID="butExport" runat="server" Text="Export Excel" OnClick="butExport_Click" />
  <asp:Label ID="Label2" runat="server" Width="170px" BackColor="#FFFF80" BorderColor="Black"></asp:Label>&nbsp;
  </td>
  </tr>
  </table> 
  <dx:ASPxGridView ID="ASPxGridView1" runat="server" Width="872px" AutoGenerateColumns="False">
  <Columns>
  <dx:GridViewCommandColumn ShowSelectCheckbox="True" VisibleIndex="0" Width="30px">
  <ClearFilterButton Visible="True">
  </ClearFilterButton>
  <HeaderStyle HorizontalAlign="Center" />

  <HeaderTemplate>
  <input id="Checkbox1" type="checkbox" onclick="ASPxGridView1.SelectAllRowsOnPage(this.checked);" />
  </HeaderTemplate>
  </dx:GridViewCommandColumn>
  <dx:GridViewDataTextColumn Caption="Orderid" VisibleIndex="1" FieldName="Order_id">
  </dx:GridViewDataTextColumn>
  <dx:GridViewDataTextColumn Caption="Itemid" VisibleIndex="2" FieldName="Item_ID">
  </dx:GridViewDataTextColumn>
  <dx:GridViewDataTextColumn Caption="FactoryCode" VisibleIndex="3" FieldName="Factory_Code">
  </dx:GridViewDataTextColumn>
  <dx:GridViewDataTextColumn Caption="ImportDate" VisibleIndex="4" FieldName="Data_entry_Date">
  </dx:GridViewDataTextColumn>
  <dx:GridViewDataTextColumn Caption="Fob" VisibleIndex="5" FieldName="Fob_Code">
  </dx:GridViewDataTextColumn>
  <dx:GridViewDataTextColumn Caption="AutoID" FieldName="AutoID" VisibleIndex="6">
  </dx:GridViewDataTextColumn>
  </Columns>
  <SettingsPager PageSize="50">
  </SettingsPager>
  </dx:ASPxGridView>  
  <ajaxToolkit:PopupControlExtender ID="PopupControlExtender1" runat="server" PopupControlID="UpdatePanel1" TargetControlID="btnMore">
  </ajaxToolkit:PopupControlExtender>
  <asp:Panel ID="Panel1" runat="server" Height="92px" Width="233px">
  <table border="0" cellpadding="0" cellspacing="0" width="180" style="background-color=DarkSeaGreen">
  <tr>
  <td>
  <asp:RadioButton ID="Rad1" runat="server" GroupName="Pop" Text="Order_ID" Width="80px" />  
  <asp:RadioButton ID="Rad2" runat="server" GroupName="Pop" Text="Item_ID" Width="80px" /></td></tr>
  <tr><td>
  <asp:TextBox ID="txtWh" runat="server" Height="136px" TextMode="MultiLine" Width="160px"></asp:TextBox>
  </td></tr>
  <tr><td>
  <asp:Button ID="btClearTxt" runat="server" Text="ClearText" /></td></tr>
  </table>
  </asp:Panel>
  <ajaxToolkit:CalendarExtender ID="CalendarExtender1" runat="server" Format="yyyy-MM-dd"
  PopupButtonID="txtFrom" TargetControlID="txtFrom">
  </ajaxToolkit:CalendarExtender>
  <dx:ASPxGridViewExporter id="ASPxGridViewExporter1" runat="server" ExportedRowType="Selected"
  GridViewID="ASPxGridView1">
  </dx:ASPxGridViewExporter>

  </div>  
  </ContentTemplate>
  </asp:UpdatePanel>
</asp:Content>


[解决办法]
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