JavaScriptSerializer 序列化json 时间格式

Model m = new Model { Id = 1, Dt = DateTime.Now };
        JavaScriptSerializer js = new JavaScriptSerializer();
        string str = js.Serialize(m);
        str = Regex.Replace(str, @"\\/Date\((\d+)\)\\/", match => 
        {
            DateTime dt = new DateTime(1970, 1, 1);
            dt = dt.AddMilliseconds(long.Parse(match.Groups[1].Value));
            dt = dt.ToLocalTime();
           return dt.ToString("yyyy-MM-dd HH:mm:ss");
        });
        Response.Write(str);
//{"Id":1,"Dt":"2011-08-17 17:38:47"} 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;   
using System.Runtime.Serialization.Json;   
using System.IO;   
using System.Text;   
using System.Text.RegularExpressions;   
/// <summary>  
/// JSON序列化和反序列化辅助类  
/// </summary>  
public class JsonHelper  
{  
     /// <summary>  
    /// JSON序列化  
    /// </summary>  
     public static string JsonSerializer<T>(T t)  
     {  
         DataContractJsonSerializer ser = new DataContractJsonSerializer(typeof(T));  
         MemoryStream ms = new MemoryStream();  
        ser.WriteObject(ms, t);  
         string jsonString = Encoding.UTF8.GetString(ms.ToArray());  
         ms.Close();  
         //替换Json的Date字符串  
         string p = @"///Date/((/d+)/+/d+/)///"; /*////Date/((([/+/-]/d+)|(/d+))[/+/-]/d+/)////*/
         MatchEvaluator matchEvaluator = new MatchEvaluator(ConvertJsonDateToDateString);  
          Regex reg = new Regex(p);  
         jsonString = reg.Replace(jsonString, matchEvaluator);  
         return jsonString;  
     }  
     /// <summary>  
     /// JSON反序列化  
     /// </summary>  
     public static T JsonDeserialize<T>(string jsonString)  
     {  
         //将"yyyy-MM-dd HH:mm:ss"格式的字符串转为"//Date(1294499956278+0800)//"格式  
         string p = @"/d{4}-/d{2}-/d{2}/s/d{2}:/d{2}:/d{2}";  
        MatchEvaluator matchEvaluator = new MatchEvaluator(ConvertDateStringToJsonDate);  
        Regex reg = new Regex(p);  
         jsonString = reg.Replace(jsonString, matchEvaluator);  
         DataContractJsonSerializer ser = new DataContractJsonSerializer(typeof(T));  
        MemoryStream ms = new MemoryStream(Encoding.UTF8.GetBytes(jsonString));  
         T obj = (T)ser.ReadObject(ms);  
         return obj;  
     }  
    
     /// <summary>  
     /// 将Json序列化的时间由/Date(1294499956278+0800)转为字符串  
     /// </summary>  
     private static string ConvertJsonDateToDateString(Match m)  
     {  
         string result = string.Empty;  
         DateTime dt = new DateTime(1970,1,1);  
         dt = dt.AddMilliseconds(long.Parse(m.Groups[1].Value));  
         dt = dt.ToLocalTime();  
         result = dt.ToString("yyyy-MM-dd HH:mm:ss");  
        return result;  
     }  
     /// <summary>  
     /// 将时间字符串转为Json时间  
     /// </summary>  
     private static string ConvertDateStringToJsonDate(Match m)  
     {  
         string result = string.Empty;  
         DateTime dt = DateTime.Parse(m.Groups[0].Value);  
         dt = dt.ToUniversalTime();  
         TimeSpan ts = dt - DateTime.Parse("1970-01-01");  
         result = string.Format("///Date({0}+0800)///",ts.TotalMilliseconds);  
        return result;  
    }  
 }