jquery gridview中checkbox状态失灵

jquery gridview中checkbox状态失效
 $.each($("#ctl00_MainContent_smtSutPerList").find("tr"), function (index, obj) {
                    if (index != 0) {
                        var object = $(this).find("td").eq(12).find($(":checkbox"));
                        alert(object.is(':checked'));
                        if (object.is(':checked') == true) {
                            count += 1;
                        }
                    }
                }); jquery?gridview jquery
[解决办法]

$("#ctl00_MainContent_smtSutPerList").find("input [type=checkbox]").each(function(i)
{
    if($(this).attr("checked"))
      count++;
});