asp.net javascript实现页面局部（不知道局部还是无）刷新

简单实现代码如下：
var xmlhttp;
if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp = new XMLHttpRequest();
}
else {// code for IE6, IE5
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange = function () {
if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
//局部刷新代码 }
}
xmlhttp.open("get", "StatutoryDayCheck.aspx?dates=" + encodeURIComponent(dates), true);
xmlhttp.send();