CascadingDropDown问题??

Question

<asp:UpdatePanel ID="UpdatePanel1" runat="server">
  <ContentTemplate>
    <asp:DropDownList ID="ddlProvince" runat="server">
    </asp:DropDownList><ajax:CascadingDropDown ID="CascadingDropDown2" runat="server" TargetControlID="ddlProvince" ServicePath="SNWebService.asmx" ServiceMethod="GetProvinceContents" Category="Province" PromptText="请选择省份" LoadingText="省份加载中...">
    </ajax:CascadingDropDown>
    .......      
  </ContentTemplate>
</asp:UpdatePanel>
<asp:Button ID="btn" runat="server" Text="submit" OnClick="btnok" />
按钮Btn代码放在UpDatePanel中,单击按钮提交就出错而按钮Btn代码放在UpDatePanel外,单击按钮提交就正常

Answer 1

楼上的,要怎样写才正确,谢谢!!!