简单的ajax获取json

一个DBhelper类，用来操作数据库

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;

namespace JsonTest.helper
{
    public class DBhelper
    {
        public static string ConnectStrings;

public static void GetConnectStr()
        {
            ConnectStrings = System.Configuration.ConfigurationManager.ConnectionStrings["ConnectionStr"].ConnectionString;
        }
        public static SqlDataReader GetCommentByID(int id,string sql)
        {
            GetConnectStr();
            SqlDataReader rs = null;
            try
            {
                SqlConnection con = new SqlConnection(ConnectStrings);
                con.Open();
                SqlCommand com = new SqlCommand(sql, con);
                rs=com.ExecuteReader();
            }
            catch (Exception err)
            {
                throw err;
            }
            return rs;
        }
    }
};

前台htm页发出ajax post请求

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title></title>
    <script type="text/javascript" src="Scripts/jquery-1.4.1.js"></script>
    <script type="text/javascript">
        $(document).ready(function () {
            $("#button1").click(function sys() {
                $.post("html_1.ashx", { "ID": 1 }, function sys(json) {
                    var str = json.item1 + json.item2 + json.item3 + json.item4;
                    $("ul").append("<li>" + str + "</li>");
                }, "json");
            });
        });        
    </script>
</head>
<body>
    <input type="button" id="button1" value="点击" />
    <ul>
    </ul>
</body>
</html>

后台ashx处理程序处理请求

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data;
using System.Data.SqlClient;
using JsonTest.helper;
using System.Web.Script.Serialization;

namespace JsonTest
{  
    /// <summary>
    /// html_1 的摘要说明
    /// </summary>
    public class html_1 : IHttpHandler
    {

public void ProcessRequest(HttpContext context)
        {
            context.Response.ContentType = "text/plain";
            int id = Convert.ToInt32(context.Request["ID"]);
            string sql = "select * from item where ItemID=" + id + "";
            SqlDataReader sdr = null;
            sdr=DBhelper.GetCommentByID(id, sql);
            item Item = new item();
            while (sdr.Read())
            {

Item.item1 = sdr[0].ToString();
                Item.item2 = sdr[1].ToString();
                Item.item3 = sdr[2].ToString();
                Item.item4 = sdr[3].ToString();
            }
            sdr.Close();
            sdr = null;
            JavaScriptSerializer js = new JavaScriptSerializer();
            string json = js.Serialize(Item).ToString();
            context.Response.Write(json);
        }

public bool IsReusable
        {
            get
            {
                return false;
            }
        }

public class item
        {
            public string item1;
            public string item2;
            public string item3;
            public string item4;
        }
    }
}

这样就可以无刷新的实现