服务器的button控件点击没有反应
                        <form id="from1" runat="server" method="post">
                            <table>
                                <tr>
                                    <th >请输入提取码:</th>
                                    <td>
                                        <input class="access-code access-fld" id="code" name="accessCode" type="text" /></td>
                                </tr>
                                <tr>
                                    <th></th>
                                    <th rowspan="2">
                                        <asp:Button ID="Button2" runat="server" Text="下载文件" OnClick="Button2_Click" />
                                    </th>