<link rel="stylesheet" type="text/css" href="../Styles/icon.css" />
 <script src="../Scripts/jquery-1.7.1.min.js" type="text/javascript"></script>
 <script type="text/javascript" src="../Scripts/jquery.easyui.min.js"></script>
 
<input class="easyui-combobox" id="txtDwmc" runat="server"  size="50" data-options="valueField:'id',textField:'dwmc',url:'../handler/combobox_data.ashx'" />
--../handler/combobox_data.ashx   返回Json格式文件
 $(function () {
  $('#txtDwmc').combobox({
                onChange: function (n, o) {
                   var companyId = $('#txtDwmc').combobox('getValue');//获取改变的值
                   alert(companyId );
                }
            });