a

#region DataTable转Json
        /// <summary>
        /// 将DataTable中的数据转换为JSON字符串，只返回[{...},{...},{...}...]的数据，没有表名
        /// </summary>
        /// <param name="dt">要转JSON的DataTable</param>
        /// <returns></returns>
        public static String ToJson(DataTable dt)
        {
            if (dt != null && dt.Rows.Count > 0 && dt.Columns.Count > 0)
            {
                StringBuilder _sbRow = new StringBuilder();
                StringBuilder _sbCol = new StringBuilder();
                foreach (DataRow dr in dt.Rows)
                {
                    if (_sbRow.Length > 0)
                        _sbRow.Append(",");
                    _sbRow.Append("{");
                    foreach (DataColumn dc in dt.Columns)
                    {
                        if (_sbCol.Length > 0)
                            _sbCol.Append(",");
                        _sbCol.Append("\"" + dc.ColumnName + "\":\"" + dr[dc].ToString() + "\"");
                    }
                    _sbRow.Append(_sbCol);
                    _sbRow.Append("}");
                    _sbCol.Length = 0;//将列清空
                }
                return "[" + _sbRow + "]";
            }
            return "[]";
        }
        #endregion

#region list<>转Json
public static string ListToJson<T>(IList<T> list, string jsonName)
        {
            StringBuilder Json = new StringBuilder();
            if (string.IsNullOrEmpty(jsonName))
                jsonName = list[0].GetType().Name;
            Json.Append("{\"" + jsonName + "\":[");
            if (list.Count > 0)
            {
                for (int i = 0; i < list.Count; i++)
                {
                    T obj = Activator.CreateInstance<T>();
                    PropertyInfo[] pi = obj.GetType().GetProperties();
                    Json.Append("{");
                    for (int j = 0; j < pi.Length; j++)
                    {
                        Type type = pi[j].GetValue(list[i], null).GetType();
                        Json.Append("\"" + pi[j].Name.ToString() + "\":" + "\""+String.Format(pi[j].GetValue(list[i], null).ToString()+"\"", type));

if (j < pi.Length - 1)
                        {
                            Json.Append(",");
                        }
                    }
                    Json.Append("}");
                    if (i < list.Count - 1)
                    {
                        Json.Append(",");
                    }
                }
            }
            Json.Append("]}");
            return Json.ToString();
        }
#endregion

$.ajax格式
$.ajax({
     type: "post",
     url: "restTestPage.aspx/sayHi",
     contentType: "application/json; charset=utf-8",
     dataType: "json",
     data: "{'bookName':'" + bookName + "','nowPage':'" + nowPage + "'}",
     success: function (data) {
     alert(data.d);
     //var json = $.parseJSON(data.d);
     //$.each(json.jsonName, function (idx, json) {
     //    alert(json.SSH);
     //})
    },
    error: function (XMLHttpRequest, textStatus, errorThrown) {
    var err=XMLHttpRequest.status;
    if (err == '500') {
            alert(textStatus);
            alert(XMLHttpRequest.status);
            alert(XMLHttpRequest.readyState);
            alert(XMLHttpRequest.responseText);
       }
   }
});

list 转 DataTable
[csharp] view plaincopyprint?
List<info> infos = Dal.GetInfos();  
        DataTable dt = new DataTable();  
        dt.Columns.Add("cName");  
 
        foreach (var info in infos)  
        {  
            DataRow dr = dt.NewRow();  
            dr["cName"] = info.Name;  
            dt.Add(dr);  
        }

网上的:
 
[csharp] view plaincopyprint?
public static class DataTableExtensions  
{  
    /// <summary>    
 
    /// 转化一个DataTable    
 
    /// </summary>    
 
    /// <typeparam name="T"></typeparam>    
    /// <param name="list"></param>    
    /// <returns></returns>    
    public static DataTable ToDataTable<T>(this IEnumerable<T> list)  
    {  
 
        //创建属性的集合    
        List<PropertyInfo> pList = new List<PropertyInfo>();  
        //获得反射的入口    
 
        Type type = typeof(T);  
        DataTable dt = new DataTable();  
        //把所有的public属性加入到集合 并添加DataTable的列    
        Array.ForEach<PropertyInfo>(type.GetProperties(), p => { pList.Add(p); dt.Columns.Add(p.Name, p.PropertyType); });  
        foreach (var item in list)  
        {  
            //创建一个DataRow实例    
            DataRow row = dt.NewRow();  
            //给row 赋值    
            pList.ForEach(p => row[p.Name] = p.GetValue(item, null));  
            //加入到DataTable    
            dt.Rows.Add(row);  
        }  
        return dt;  
    }  
 
 
    /// <summary>    
    /// DataTable 转换为List 集合    
    /// </summary>    
    /// <typeparam name="TResult">类型</typeparam>    
    /// <param name="dt">DataTable</param>    
    /// <returns></returns>    
    public static List<T> ToList<T>(this DataTable dt) where T : class, new()  
    {  
        //创建一个属性的列表    
        List<PropertyInfo> prlist = new List<PropertyInfo>();  
        //获取TResult的类型实例  反射的入口    
 
        Type t = typeof(T);  
 
        //获得TResult 的所有的Public 属性 并找出TResult属性和DataTable的列名称相同的属性(PropertyInfo) 并加入到属性列表     
        Array.ForEach<PropertyInfo>(t.GetProperties(), p => { if (dt.Columns.IndexOf(p.Name) != -1) prlist.Add(p); });  
 
        //创建返回的集合    
 
        List<T> oblist = new List<T>();  
 
        foreach (DataRow row in dt.Rows)  
        {  
            //创建TResult的实例    
            T ob = new T();  
            //找到对应的数据  并赋值    
            prlist.ForEach(p => { if (row[p.Name] != DBNull.Value) p.SetValue(ob, row[p.Name], null); });  
            //放入到返回的集合中.    
            oblist.Add(ob);  
        }  
        return oblist;  
    }  
 
 
 
 
    /// <summary>    
    /// 将集合类转换成DataTable    
    /// </summary>    
    /// <param name="list">集合</param>    
    /// <returns></returns>    
    public static DataTable ToDataTableTow(IList list)  
    {  
        DataTable result = new DataTable();  
        if (list.Count > 0)  
        {  
            PropertyInfo[] propertys = list[0].GetType().GetProperties();  
 
            foreach (PropertyInfo pi in propertys)  
            {  
                result.Columns.Add(pi.Name, pi.PropertyType);  
            }  
            for (int i = 0; i < list.Count; i++)  
            {  
                ArrayList tempList = new ArrayList();  
                foreach (PropertyInfo pi in propertys)  
                {  
                    object obj = pi.GetValue(list[i], null);  
                    tempList.Add(obj);  
                }  
                object[] array = tempList.ToArray();  
                result.LoadDataRow(array, true);  
            }  
        }  
        return result;  
    }  
 
 
    /**/  
 
    /// <summary>    
    /// 将泛型集合类转换成DataTable    
 
    /// </summary>    
    /// <typeparam name="T">集合项类型</typeparam>    
 
    /// <param name="list">集合</param>    
    /// <returns>数据集(表)</returns>    
    public static DataTable ToDataTable<T>(IList<T> list)  
    {  
        return ToDataTable<T>(list, null);  
 
    }  
 
 
    /**/  
 
    /// <summary>    
    /// 将泛型集合类转换成DataTable    
    /// </summary>    
    /// <typeparam name="T">集合项类型</typeparam>    
    /// <param name="list">集合</param>    
    /// <param name="propertyName">需要返回的列的列名</param>    
    /// <returns>数据集(表)</returns>    
    public static DataTable ToDataTable<T>(IList<T> list, params string[] propertyName)  
    {  
        List<string> propertyNameList = new List<string>();  
        if (propertyName != null)  
            propertyNameList.AddRange(propertyName);  
        DataTable result = new DataTable();  
        if (list.Count > 0)  
        {  
            PropertyInfo[] propertys = list[0].GetType().GetProperties();  
            foreach (PropertyInfo pi in propertys)  
            {  
                if (propertyNameList.Count == 0)  
                {  
                    result.Columns.Add(pi.Name, pi.PropertyType);  
                }  
                else  
                {  
                    if (propertyNameList.Contains(pi.Name))  
                        result.Columns.Add(pi.Name, pi.PropertyType);  
                }  
            }  
 
            for (int i = 0; i < list.Count; i++)  
            {  
                ArrayList tempList = new ArrayList();  
                foreach (PropertyInfo pi in propertys)  
                {  
                    if (propertyNameList.Count == 0)  
                    {  
                        object obj = pi.GetValue(list[i], null);  
                        tempList.Add(obj);  
                    }  
                    else  
                    {  
                        if (propertyNameList.Contains(pi.Name))  
                        {  
                            object obj = pi.GetValue(list[i], null);  
                            tempList.Add(obj);  
                        }  
                    }  
                }  
                object[] array = tempList.ToArray();  
                result.LoadDataRow(array, true);  
            }  
        }  
        return result;  
    }  
}

-----------------------------------------------------------------------------------------------------

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="StudentManage.aspx.cs" Inherits="N09_Chapter6.StudentManage" %>

<!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 runat="server">
    <title></title>
    <script src="jquery1.8/jquery-1.8.0.js" type="text/javascript"></script>
    <script src="jquery1.8/json2.js" type="text/javascript"></script>
    <script type="text/javascript">
        $(function () {
            $("#btnShowAllStudents").click(function () {
                $.ajax({
                    url: "StudentWebService.asmx/GetAllStudents",
                    type: "post",
                    data: {}, //将参数对象转换为字符串
                    contentType: "application/json",
                    dataType: "json",
                    success: function (data) {
                        var students = data.d;
                        var result = "<tr><th>学号</th><th>姓名</th><th>性别</th><th>分数</th><th>年龄</th><th>操作</th></tr>";
                        for (var i = 0; i < students.length; i++) {
                            result += "<tr>";
                            result += "<td>" + students[i].StuNo + "</td>";
                            result += "<td>" + students[i].Name + "</td>";
                            result += "<td>" + students[i].Sex + "</td>";
                            result += "<td>" + students[i].Score + "</td>";
                            result += "<td>" + students[i].Age + "</td>";
                            result += "<td><a href='#' onclick='getStudentByNo(" + students[i].StuNo + ")'>修改</a>|<a href='#' onclick='deleteStudent(" + students[i].StuNo + ")'>删除</a></td>";
                            result += "</tr>";
                        }
                        $("#tb_students").html(result);
                    },
                    error: function () {
                        alert("ajax请求失败！");
                    }
                });
            });
        });
        //根据学号获取学员信息并填充到修改学员信息的表单元素中
        function getStudentByNo(stuNo) {
            $("#divOp").show();
            $("#txtStuNo").attr("readonly", true);
            $("#btnAdd").hide();
            $("#btnUpdate").show();
            //根据学号查询相应信息
            $.ajax({
                url: "StudentWebService.asmx/GetStuInfoByStuNo",
                type: "post",
                data: "{'stuNo':" + stuNo + "}",
                contentType: "application/json",
                dataType: "json",
                success: function (data) {
                    var result = data.d;
                    $("#txtStuNo").val(result.StuNo);
                    $("#txtName").val(result.Name);
                    $("[name=sex]").each(function (i, data) {
                        if (data.value == result.Sex) {
                            data.checked = true;
                            return;
                        }
                    });
                    $("#txtScore").val(result.Score);
                    $("#txtAge").val(result.Age);
                },
                error: function () {
                    alert("发送ajax请求失败！");
                }
            });

}
        //修改学员信息
        function updateStudent() {
            var stuNo = $("#txtStuNo").val();
            var stuName = $("#txtName").val();
            var stuSex = $("[name=sex]:checked").val();
            var stuScore = $("#txtScore").val();
            var stuAge = $("#txtAge").val();
            var stuInfo = { "StuNo": stuNo, "Name": stuName, "Sex": stuSex, "Score": stuScore, "Age": stuAge };
            var param = new Object();
            param.student = stuInfo;
            $.ajax({
                url: "StudentWebService.asmx/UpdateStuInfo",
                type: "post",
                data: JSON.stringify(param),
                contentType: "application/json",
                dataType: "json",
                success: function (data) {
                    if (data) {
                        alert("修改成功！");
                        $("#btnShowAllStudents").click();
                    } else {
                        alert("修改失败！");
                    }
                },
                error: function () {
                    alert("发送ajax请求失败！");
                }
            });
        }
        //根据学号删除学员信息
        function deleteStudent(stuNo) {            
            if(confirm("确定要删除吗？")){
                $.ajax({
                    url: "StudentWebService.asmx/DeleteStuInfo",
                    type: "post",
                    data: "{'stuNo':" + stuNo + "}",
                    contentType: "application/json",
                    dataType: "json",
                    success: function (data) {
                        if (data) {
                            alert("删除成功！");
                            $("#btnShowAllStudents").click();
                        } else {
                            alert("删除失败！");
                        }
                    },
                    error: function () {
                        alert("发送ajax请求失败！");
                    }
                });
            }
        }
        //显示添加学员的div
        function showAddStudentDiv() {
            $("#divOp").show();
            $("#btnAdd").show();
            $("#btnUpdate").hide();
            $("#txtStuNo").val("");
            $("#txtName").val("");
            $("[name=sex]:eq(0)").attr("checked", true);
            $("#txtScore").val("");
            $("#txtAge").val("");
        }
        //添加学员信息
        function addStudent() {
            var stuNo = $("#txtStuNo").val();
            var stuName = $("#txtName").val();
            var stuSex = $("[name=sex]:checked").val();
            var stuScore = $("#txtScore").val();
            var stuAge = $("#txtAge").val();
            var stuInfo = { "StuNo": stuNo, "Name": stuName, "Sex": stuSex, "Score": stuScore, "Age": stuAge };
            var param = new Object();
            param.student = stuInfo;
            $.ajax({
                url: "StudentWebService.asmx/AddStudent",
                type: "post",
                data: JSON.stringify(param),
                contentType: "application/json",
                dataType: "json",
                success: function (data) {
                    if (data) {
                        alert("添加成功！");
                        $("#btnShowAllStudents").click();
                    } else {
                        alert("添加失败！");
                    }
                },
                error: function () {
                    alert("发送ajax请求失败！");
                }
            });
        }
        //根据性别查询学员信息
        function selectStuInfoBySex() {
            var sex = $("#selSex").val();//获取选中的性别
            $.ajax({
                url: "StudentWebService.asmx/GetStuInfoBySex",
                type: "post",
                data: "{'sex':'" + sex + "'}",
                contentType: "application/json",
                dataType: "json",
                success: function (data) {
                    var students = data.d;
                    var result = "<tr><th>学号</th><th>姓名</th><th>性别</th><th>分数</th><th>年龄</th><th>操作</th></tr>";
                    for (var i = 0; i < students.length; i++) {
                        result += "<tr>";
                        result += "<td>" + students[i].StuNo + "</td>";
                        result += "<td>" + students[i].Name + "</td>";
                        result += "<td>" + students[i].Sex + "</td>";
                        result += "<td>" + students[i].Score + "</td>";
                        result += "<td>" + students[i].Age + "</td>";
                        result += "<td><a href='#' onclick='getStudentByNo(" + students[i].StuNo + ")'>修改</a>|<a href='#' onclick='deleteStudent(" + students[i].StuNo + ")'>删除</a></td>";
                        result += "</tr>";
                    }
                    $("#tb_students").html(result);
                },
                error: function () {
                    alert("发送ajax请求失败！");
                }
            });
        }
    </script>
</head>
<body>
    <input type="button" value="显示所有学员信息" id="btnShowAllStudents" />
    性别：
    <select id="selSex" onchange="selectStuInfoBySex()">
        <option>--请选择性别--</option>
        <option value="男">男</option>
        <option value="女">女</option>
    </select>
    <table id="tb_students" border="1">
    </table>
    <input type="button" value="添加学员信息" id="btnAddStudent" onclick="showAddStudentDiv()"/>
    <div id="divOp" style="border:1px solid gray; width:500px; height:100px;display:none">
        <form id="stuForm">
            学号：<input type="text" id="txtStuNo"/>
            姓名：<input type="text" id="txtName" /><br />
            性别：<input type="radio" name="sex" value="男" checked/>男<input type="radio" name="sex" value="女"/>女<br />
            成绩：<input type="text" id="txtScore" />
            年龄：<input  type="text" id="txtAge"/><br />
            <input type="button"  value="添加" id="btnAdd" onclick="addStudent()"/>
            <input type="button"  value="修改" id="btnUpdate" onclick="updateStudent()"/>
        </form>
    </div>
</body>
</html>
------------------------------asmx----------------------------

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;

namespace N09_Chapter6
{
    /// <summary>
    /// StudentWebService 的摘要说明
    /// </summary>
    [WebService(Namespace = "http://tempuri.org/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
    [System.ComponentModel.ToolboxItem(false)]
    // 若要允许使用 ASP.NET AJAX 从脚本中调用此 Web 服务，请取消对下行的注释。
    [System.Web.Script.Services.ScriptService]
    public class StudentWebService : System.Web.Services.WebService
    {
        /// <summary>
        /// 获取所有学员信息
        /// </summary>
        /// <returns></returns>
        [WebMethod]
        public List<StuInfo> GetAllStudents()
        {
            JqueryDBDataContext db = new JqueryDBDataContext();
            return db.StuInfo.ToList();
        }
        /// <summary>
        /// 添加学员信息
        /// </summary>
        /// <param name="student">学员对象</param>
        /// <returns></returns>
        [WebMethod]
        public bool AddStudent(StuInfo student)
        {
            try
            {
                JqueryDBDataContext db = new JqueryDBDataContext();
                db.StuInfo.InsertOnSubmit(student);
                db.SubmitChanges();
                return true;
            }
            catch (Exception)
            {
                return false;
            }
        }
        /// <summary>
        /// 根据学号获取学员信息
        /// </summary>
        /// <param name="stuNo">学号</param>
        /// <returns></returns>
        [WebMethod]
        public StuInfo GetStuInfoByStuNo(int stuNo)
        {
            JqueryDBDataContext db = new JqueryDBDataContext();
            return db.StuInfo.FirstOrDefault(s=>s.StuNo==stuNo);
        }
        /// <summary>
        /// 修改学员信息
        /// </summary>
        /// <param name="student">学员信息</param>
        /// <returns></returns>
        [WebMethod]
        public bool UpdateStuInfo(StuInfo student)
        {
            try
            {
                JqueryDBDataContext db = new JqueryDBDataContext();
                StuInfo stu = db.StuInfo.FirstOrDefault(s => s.StuNo == student.StuNo);
                stu.Name = student.Name;
                stu.Sex = student.Sex;
                stu.Age = student.Age;
                stu.Score = student.Score;
                db.SubmitChanges();
            }
            catch (Exception ex)
            {
                return false;
            }
            return true;
        }
        /// <summary>
        /// 删除学员信息
        /// </summary>
        /// <param name="stuNo">学号</param>
        /// <returns></returns>
        [WebMethod]
        public bool DeleteStuInfo(int stuNo)
        {
            try
            {
                JqueryDBDataContext db = new JqueryDBDataContext();
                StuInfo stu = db.StuInfo.FirstOrDefault(s => s.StuNo == stuNo);
                db.StuInfo.DeleteOnSubmit(stu);
                db.SubmitChanges();
            }
            catch (Exception  ex)
            {
                return false;
            }
            return true;
        }
        /// <summary>
        /// 根据性别获取学员信息
        /// </summary>
        /// <param name="sex"></param>
        /// <returns></returns>
        [WebMethod]
        public List<StuInfo> GetStuInfoBySex(string sex)
        {
            JqueryDBDataContext db = new JqueryDBDataContext();
            return db.StuInfo.Where(s=>s.Sex.ToString()==sex).ToList();
        }
    }
}
------------------------------------------------