....
            ds.RemotingFormat = SerializationFormat.Xml;
            SoapFormatter fmt = new SoapFormatter();
            MemoryStream ms = new MemoryStream();
            fmt.Serialize(ms, ds);
            return ms.ToArray();

    [DataContract]
    public class CountryType
    {
        private decimal _countryID;
        [DataMember]
        public decimal CountryID
        {
            get { return _countryID; }
            set { _countryID = value; }
        }
........