ajax请求的有关问题。无法获取到传递过来的参数_ASP.NET

ajax请求的问题。无法获取到传递过来的参数

JScript code

                $.ajax({                    type: "POST",                    url: "ValueChange.ashx",                    data: { sm: logInfo },                    contentType: "application/text; charset=utf-8",                    success: function() {                        var session = '<%=Session["aa"]%>';                        alert(session);                        return true;                    }                });

C# code

using System;using System.Collections;using System.Data;using System.Linq;using System.Web;using System.Web.Services;using System.Web.Services.Protocols;using System.Xml.Linq;using System.Web.SessionState;namespace ValueChangePro{    /// <summary>    /// $codebehindclassname$ 的摘要说明    /// </summary>    [WebService(Namespace = "http://tempuri.org/")]    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]    public class Handler1 : IHttpHandler, IRequiresSessionState    {        public void ProcessRequest(HttpContext context)        {            context.Response.ContentType = "text/plain";            var log = context.Request.QueryString["sm"];            context.Session["aa"] = log;        }        public bool IsReusable        {            get            {                return false;            }        }    }}

在一般处理性文件中无法获取传递过来的sm ，firebug调试的时候可以看到他的参数
sm=TextBox2%EF%BC%9A+%E7%94%B1+%22%22++%E8%A2%AB%E4%BF%AE%E6%94%B9%E4%B8%BA++%22sdfsd%22%0A
程序alert sm的值确实是有值的但是就是获取不到

------解决方案--------------------------------------------------------
data: { "sm": logInfo },

var log = context.Request.Params.Get("sm");
或
var log = context.Request.Form["sm"];