[Serializable]
    [DataContract]
    public class UserJson
    {
        [DataMember]
        public Int64 uid
        { get; set; }
        [DataMember]
        public string username
        { get; set; }
        [DataMember]
        public string pwd
        { get; set; }
    }
    public class Json
    {
        public void ReadJson(string JsonStr)
        {
            JavaScriptSerializer jss = new JavaScriptSerializer();
            UserJson userJson = jss.Deserialize<UserJson>(JsonStr);
        }
    }