//класс для хранения ключ-значение
    [DataContract]
    public class fielding
    {
        [DataMember]
        public string key { set; get; }
        [DataMember]
        public string value { set; get; }
        [DataMember]
        public string type { set; get; }
    }
    //класс список(ключ-значение)
    [DataContract]
    public class type_field
    {
        List<fielding> list = new List<fielding>();
     
        public fielding this[string key]
        {
            set
            {

                foreach (fielding f in list.ToArray())
                    if (f.key == key)
                    {
                        f.type = value.type;
                        f.value = value.value;
                    }
            }
            get
            {
                return list.Where(n => n.key == key).First();

            }
        }
    }
  [DataContract]
        public class zaivka
        {

            [DataMember]
            public type_field fields { set; get; }
.................