vs2008 ajax:AjaxPanel 页面无刷新操作

<%@ Register TagPrefix="ajax" Namespace="MagicAjax.UI.Controls" Assembly="MagicAjax" %>

...

       <ajax:AjaxPanel id="AjaxPanel2" runat="server">
                      <tr class="tdbg">
                       <td class="style1"> 企业所在地： </td>
                       <td colspan="4">&nbsp; 

                        <asp:dropdownlist id="Province" runat="server" AutoPostBack="True" onselectedindexchanged="Province_SelectedIndexChanged"></asp:dropdownlist>&nbsp;省&nbsp;
                        <asp:dropdownlist id="City" runat="server"></asp:dropdownlist>&nbsp;市

                             <font color="#FF0000">*</font> </td>
                      </tr>
               </ajax:AjaxPanel>

.....

  <ajax:AjaxPanel id="AjaxPanel1" runat="server">
    
       <tr>
        <td class="style1"><font face="宋体">经营范围大类：</font></td>
        <td colspan="4">&nbsp;<asp:DropDownList ID="ddlclass1" runat="server"
                                        AutoPostBack="True" onselectedindexchanged="ddlclass1_SelectedIndexChanged" /> <font color="#FF0000">*</font>
         </td></tr>
       <tr >
                       <td class="style1"><font face="宋体">经营范围小类：</font></td>
                       <td colspan="4">
                       <table width="100%" border="0" cellspacing="0" cellpadding="0">                     
                              <tr>
                                <td width="21%">
                                请选择经营范围小类<br />
                                 <asp:ListBox ID="lbclassa" Width="200px" Rows="7" runat="server" /></td>
                                <td width="26%">
                                请点击选择左偶合适的经营范<br>
                                      围小类，再点击下面的“<span class="r">添加</span>”<br>
                                      按钮（最多五项）。如右侧选<br>
                                      择错误，请选择后点击“删除”<br> 
                                      <asp:Button ID="btntypeadd" Text="添 加" runat="server"
                                        onclick="btntypeadd_Click" />&nbsp;&nbsp; &nbsp;&nbsp;
                                      <asp:Button ID="btntypedel" Text="删 除" runat="server"
                                        onclick="btntypedel_Click" />
                                 
                                </td>
                                <td width="24%">
                                您已经选择了以下小类<br />
                                 <asp:ListBox ID="lbclasss"  Width="186px" Rows="7" runat="server" /></td>
                                </tr>
                               </table></td></tr>
                              
                                </ajax:AjaxPanel>