ajax 验证登陆

    <script type="text/javascript" language="javascript">
        function IbtnEnter_onclick() {
            checklogin();
            return false;
        }
        function checklogin() {
            if ($("#TxtUserName").val() == "") {
                alert("用户名不能为空！");
                $("#TxtUserName").focus();
                return false;
            }
            if ($("#TxtPassword").val() == "") {
                alert("密码不能为空！");
                $("#TxtPassword").focus();
                return false;
            }
            $.ajax({
                type: "POST",
                url: "ajax/Handler.ashx?M=" + Math.random(),
                data: "username=" + $("#TxtUserName").val().toString() + "&pwd=" + $("#TxtPassword").val().toString(),
                success: function (data) {
                    if (data == "1") {
                        location.href = "index.aspx";
                        return true;
                    }
                    else {
                        alert("请确认您输入的用户名或密码输入是否正确！");
                        $("#TxtUserName").val("");
                        $("#TxtPassword").val("");
                        $("#TxtUserName").focus();
                        return false;
                    }
                }

            })
        }
    </script>

一般处理程序

<%@ WebHandler Language="C#" Class="Handler" %>

using System;
using System.Web;
using System.Data.SqlClient;
using System.Web.SessionState;//继承接口IReadOnlySessionState需要引入的命名空间

public class Handler : IHttpHandler, IRequiresSessionState
{
    SqlHelper helper = new SqlHelper();
    public void ProcessRequest(HttpContext context)
    {
        context.Response.ContentType = "text/plain";

        string username = context.Request.Params["username"].ToString().Trim();
        string pwd = context.Request.Params["pwd"].ToString().Trim();
        if (username != "" && pwd != "")
        {

            string sql = @"SELECT * FROM [USER] WHERE USERNAME='"+username+"' AND PASSWORD='"+pwd+"' ";
            if (!helper.Exists(sql))
            {
                context.Response.Write("0");
            }

            else
            {
                SqlDataReader reader = helper.ExecuteReader(sql);
                while (reader.Read())
                {
                    context.Response.Write("1");
                    context.Session["username"] = username.ToString().Trim();
                    context.Session["pwd"] = pwd.ToString().Trim();
                }
            }
            
        }
    }
 
    public bool IsReusable
    {
        get
        {
            return false;
        }
    }
}