asp.net+jquery ajax实现免刷新登录

因为工作需要研究了一下 js的ajax，下面是成果。
主要是三部分：
一、js部分 友情提示注意js部分中的 $("#btn_login")中的return false；这个可以阻止回转服务器不然还是会刷新

$(document).ready(function () {
    $("#btn_login").click(function () {
        postlogin();
        return false;
    });
});
 
function postlogin() {
    if (checkusername() && checkuserpwd()) {
        var username = $('#txt_loginname').val();
        var userpass = $('#txt_loginpass').val();
        $.post("../userlogin.x", { username: username, userpass: userpass }, function (result) {
            if (result == "1") {
                alert("登录成功！");
            } else if (result == "3") {
                alert("用户名不正确!");
            } else if (result == "2") {
                alert("密码不正确!");
            } else {
                alert("登录失败!请重试!" + result);
            }
        });
    }
}
 
function checkusername() {
    if ($("#txt_loginname").val().length == 0) {
        alert('用户名不能为空!');
        return false;
    } else {
        return true;
    }
}
 
function checkuserpwd() {
    if ($("#txt_loginpass").val().lenght == 0) {
        alert('密码不正确!');
        return false;
    } else {
        return true;
    }
}
二、页面部分

<table width="100%" border="0" cellspacing="0" cellpadding="0">
          <tr>
            <td width="32%" height="37" valign="middle">用户名：</td>
            <td width="68%" valign="middle">
                <input type="text" name="txt_loginname" id="txt_loginname" class="input_1"/>
            </td>
          </tr>
          <tr>
            <td height="37" valign="middle">密　码：</td>
            <td valign="middle">
            <input type="password" name="txt_loginpass" id="txt_loginpass" class="input_2"/>
            </td>
          </tr>
          <!--<tr>
            <td height="37" valign="middle">验证码：</td>
            <td valign="middle">
              <input type="text" name="textfield3" id="textfield3" class="input_3" style="float:left"/>
              <span style="float:left; margin-left:6px;"><img src="images/img_7.gif" /></span></td>
          </tr>-->
          <tr>
            <td colspan="2">
              <input type="image" name="btn_login" id="btn_login" src="images/img_4.gif" />
              <input type="image" name="input" src="images/img_5.gif" />
               <input type="image" name="input" src="images/img_6.gif" />
            </td>
          </tr>
        </table>
三、后台部分也就是在js中转向的处理登录信息的页面

protected void page_load(object sender, eventargs e)
        {
            string username = request.form["username"];
            string userpass = request.form["userpass"];
            t_user user = usermanager.loginpassword(username, userpass);
            if (user != null)
            {
                session["user"] = user;
                response.write("1");  //登录成功
                response.end();
 
            }
            else
            {
                if (usermanager.onlyone(username) >= 1)
                {
                    response.write("2");  //密码不正确
                    response.end();
                }
                else
                {
                    response.write("3");  //用户名不存在
                    response.end();
                }
            }
        }
　　
 

 

摘自 +-/\-+