包含时间的Json序列化

 public static string ObjectToJson<T>(T t)
        {
            using (MemoryStream ms = new MemoryStream())
            {
                DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(T));
                serializer.WriteObject(ms, t);
                ms.Position = 0;
                using (StreamReader reader = new StreamReader(ms))
                {
                    string json = reader.ReadToEnd();
                    string p = @"\/Date((d+)+d+)\/";
                    MatchEvaluator evaluator = new MatchEvaluator(ConvertJsonDataToDataString);
                    Regex reg = new Regex(p);
                    json = reg.Replace(json, evaluator);
                    return json;
                }
            }

        }

        public static T JsonToObject<T>(string json)
        {
            string p = @"d{4}-d{2}-d{2}sd{2}:d{2}:d{2}";
            MatchEvaluator evaluator = new MatchEvaluator(ConvertDateStringToJsonDate);    //对时间进行处理
            Regex reg = new Regex(p);
            json = reg.Replace(json, evaluator);
            using (MemoryStream ms = new MemoryStream(Encoding.Unicode.GetBytes(json)))
            {
                DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(T));
                T data = (T)serializer.ReadObject(ms);
                return data;
            }
        }

        /// <summary>
        /// 将Json时间转换为时间字符
        /// </summary>
        /// <param name="m"></param>
        /// <returns></returns>
        private static string ConvertJsonDataToDataString(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>
        /// 将时间字符转换成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;
        }

 [DataContract]
    public class RecentVisitors
    {
        [DataMember]
        public long UserId { get; set; }
        [DataMember]
        public string UserName { get; set; }
        [DataMember]
        public DateTime Dt { get; set; }
    }

var jsonStr="[{"UserId":"123123","UserName":"小小苏","Dt":"2012-09-25 10:50:00"},{"UserId":"456456","UserName":"大头","Dt":"2012-09-25 10:50:00"}]";

调用：
1：JsonToObject<List<RecentVisitors>>(jsonStr)
2：ObjectToJson<List<RecentVisitors>>(new List<RecentVisitors);