two requests are posting on reloading the data in combobox on select of another

[kush]

Hi,
    I have a requirement of OnSelect of one Combobx I should load dynamic data in another combo box.While doing so request is posting twice one post and one get.Please have a look of my both comboboxes and give your valid inputs.

<input id="dmn" class="easyui-combobox" data-options="valueField:'id',textField:'text',url:'/demand?action=get_domain_list',
        onSelect: function(rec){
          var url = '/demand?action=get_subdomain_list?id='+rec.id;
          $('#sub_Dmn').combobox('reload', url);
        }">

<input id="sub_Dmn" class="easyui-combobox" data-options="valueField:'id',textField:'text',url:'/demand?action=get_subdomain_list'">

[kush]

Awaiting for your valuable response