DataList控件中有个Panel控件，Panel控件中有个TextBox控件，如何得到文本框中输入的字？？

前台代码：
！<asp:DataList ID="DataListMyMessageBoard" runat="server" Width="100%" 
             onitemcommand="DataListMyMessageBoard_ItemCommand">
                     <HeaderTemplate>
                            <table width ="100%">
                                <tr class ="styleTrI  ">
                                 <td class ="stylePane9 ">
                                        关心指数</td>
                                    <td class ="stylePaneC ">
                                        留言人头像</td>
                                    <td class ="stylePane9 ">
                                        留言人姓名</td>
                                    <td class="stylePaneC">
                                        留言主题</td>
                                    <td class ="stylePane9 ">
                                        留言内容</td>
                                    <td class ="stylePaneC ">
                                        留言时间</td>
                                </tr>
                        </HeaderTemplate>
                        <ItemTemplate>
                                <tr class ="styleTrII ">
                                    <td class ="stylePaneC ">
                                        <asp:Label ID="lblUserID" runat="server" Text='<%# Eval("UserID") %>'></asp:Label>
                                    </td>
                                    <td class ="stylePane9 ">
                                        <asp:Image ID="imgHead" runat="server"  
                                            ImageUrl='<%# @"~\Uploads\"+Eval("ImageHead") %>' Width="114px"></asp:Image>
                                    </td>
                                    <td class ="stylePaneC ">
                                        <asp:Label ID="lblLeavePetName" runat="server" Text='<%# Eval("PetName") %>'></asp:Label>
                                    </td>
                                    <td class ="stylePane9 ">
                                        <asp:Label ID="lblTitle" runat="server" Text='<%# Eval("Title") %>'></asp:Label>
                                    </td>
                                    <td class ="stylePaneC"> 
                                        <asp:Label ID="lblMessageContent" runat="server" 
                                            Text='<%# Eval("MessageContent") %>' ></asp:Label>
                                    </td>
                                    <td class ="stylePane9 ">
                                        <asp:Label ID="lblUserTime" runat="server" Text='<%# Eval("UserTime") %>'></asp:Label>
                                    </td>
                                </tr>
                         </table>
                                <table width ="100%">
                                    <tr >
                                        <td align="left">
                                            <asp:Panel ID="panelDispear" runat="server" Visible="False">
                                                <asp:TextBox ID="txtReply" runat="server" TextMode="MultiLine" Width="500px" Height ="50px"></asp:TextBox>
                                            </asp:Panel>
                                            <br />
                                            <asp:LinkButton ID="lnkReply" runat="server" CommandName="Reply" 
                                                Font-Overline="false">回复</asp:LinkButton>
                                            <asp:LinkButton ID="lnkSubmit" runat="server" CommandName="Submit" 
                                                Font-Overline ="false" >提交</asp:LinkButton>
                                            <asp:LinkButton ID="lnkDelete" runat="server" CommandName="Delete" 
                                                Font-Overline="false">删除</asp:LinkButton>
                                        </td>
                                    </tr>            
                        </ItemTemplate> 
                         <FooterTemplate >
                               </table>
                        </FooterTemplate>
                    </asp:DataList>后台部分代码：
  protected void DataListMyMessageBoard_ItemCommand(object source, DataListCommandEventArgs e)
    {
        if (e.CommandSource.GetType() == typeof(LinkButton))
        {
            if (((LinkButton)e.CommandSource).CommandName == "Reply")
            {
               ((Panel )e.Item .FindControl ("panelDispear")).Visible =true;
            }
            if (((LinkButton)e.CommandSource).CommandName == "Submit")
            {
                string s = ((TextBox)(((Panel)e.Item.FindControl("panelDispear")).FindControl("txtReply"))).Text.Trim();
                Response.Write(s);
            }
            if (((LinkButton)e.CommandSource).CommandName == "Delete")
            {
                
            }
        }
    }
Panel设置了隐藏属性，点回复按钮时，Panel中的TextBox文本框出现，然后再TextBox中输入文字，点提交的时候，页面为什么不会打出文本框中的字？？？？代码如上图，求高手赐教！！！