/**
            * stores an operation record in history
            */
        public void SaveRegisto(Registo reg)
        {
            if (reg == null)
                return;

            SqlConnection con = new SqlConnection(connectionString);
            con.Open();
            SqlCommand query = new SqlCommand(string.Format(
                "INSERT INTO historico (op_id, op_type, old_bundle_id, new_bundle_id, old_file_id, new_file_id, tag, etiqueta) " +
                "Values ('{0}', '{1}', '{2}', '{3}', '{4}', '{5}', '{6}', getdate())",
                reg.op_id, reg.op_type, reg.old_bundle_id, reg.new_bundle_id, reg.old_file_id, reg.new_file_id, reg.tag), con);
            query.ExecuteNonQuery();

            con.Close();
        }
        /**
            * retrieves an operation record from history
            */
        public Registo GetRegisto(string op_id)
        {
            if (string.IsNullOrEmpty(op_id))
                return null;
            Registo reg = new Registo();

            SqlConnection con = new SqlConnection(connectionString);
            con.Open();
            SqlCommand query = new SqlCommand(string.Format("SELECT * FROM historico WHERE op_id = '{0}'", op_id), con);
            SqlDataReader reader = query.ExecuteReader();
            while (reader.Read()) {
                reg = new Registo(op_id,
                                  reader.GetDateTime(7), reader.GetString(1), reader.GetString(2),
                                  reader.GetString(3), reader.GetString(4), reader.GetString(5), reader.GetString(6));
            }
            reader.Close();
            con.Close();
            return reg;
        }