如何用ajax实现无刷新ASP用户登录页面

/ JScript 文件
function usersLogon()
{
var userName = document.getElementById("txtuserName").value;
var password = document.getElementById("txtpassword").value;
var checkCode = document.getElementById("txtCheckCode").value;

var response = userControl_logon.CheckCodeIsRight(checkCode).value;

if(userName == "")
{
document.getElementById("txtuserName").focus();
return false;
}
else if(password == "")
{
document.getElementById("txtpassword").focus();
return false;
}
else if(checkCode =="")
{
document.getElementById("txtCheckCode").focus();
return false;
}
else
{
if(response == true)
{
//判断用户是否存在
userControl_logon.userNameAndPasswordIsExist(u本回答被提问者采纳