获取动态控件中的值

我使用Jquery在页面上生成了一个控件
<input type='text' name='desc' value='' id='desc'/>如何在后台获得此控件中的值？一下是生成控件代码
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
     <script src="js/jquery-1.7.2.js" type="text/javascript"></script>
     <script language="javascript" type="text/javascript">
        
            $(document).ready(function () {
                //<tr/>居中
                $("#tab tr").attr("align", "center");                //增加<tr/>
                $("#but").click(function () {
                    var _len = $("#tab tr").length;
                    $("#tab").append("<tr id=" + _len + " align='center'>"
                                + "<td>" + _len + "</td>"
                                + "<td>Dynamic TR" + _len + "</td>"
                                + "<td><input type='text' name='desc" + _len + "' id='desc" + _len + "' /></td>"
                                + "<td><a href=\'#\' onclick=\'deltr(" + _len + ")\'>删除</a></td>"
                            + "</tr>");
                })
            })            //删除<tr/>
            var deltr = function (index) {
                var _len = $("#tab tr").length;
                $("tr[id='" + index + "']").remove(); //删除当前行
                for (var i = index + 1, j = _len; i < j; i++) {
                    var nextTxtVal = $("#desc" + i).val();
                    $("tr[id=\'" + i + "\']")
                .replaceWith("<tr id=" + (i - 1) + " align='center'>"
                                + "<td>" + (i - 1) + "</td>"
                                + "<td>Dynamic TR" + (i - 1) + "</td>"
                                + "<td><input type='text' name='desc" + (i - 1) + "' value='" + nextTxtVal + "' id='desc" + (i - 1) + "'/></td>"
                                + "<td><a href=\'#\' onclick=\'deltr(" + (i - 1) + ")\'>删除</a></td>"
                            + "</tr>");
                }            }
        </script></head>
<body>
    <form id="form1" runat="server">
        <table id="tab" border="1" width="60%" align="center" style="margin-top:20px">
        <tr>
            <td width="20%">序号</td>
            <td>标题</td>
            <td>描述</td>
            <td>操作</td>
       </tr>
    </table>
    <div style="border:2px; 
                border-color:#00CC00; 
                margin-left:20%;
                margin-top:20px">
        <input type="button" id="but" value="增加"/>
        <asp:Button ID="Button2" runat="server" onclick="Button2_Click" Text="Button" />
    </div>
    <input type="submit" id="but2" value="提交" />
    </form>
</body>
</html>
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