Npgsql.NpgsqlTransaction.Commit C# (CSharp) Method

        public override void Commit()
        {
            CheckDisposed();

            if (_conn == null)
            {
                throw new InvalidOperationException(resman.GetString("Exception_NoTransaction"));
            }

            NpgsqlEventLog.LogMethodEnter(LogLevel.Debug, CLASSNAME, "Commit");

            NpgsqlCommand.ExecuteBlind(_conn.Connector, "COMMIT");

            _conn.Connector.Transaction = null;
            _conn = null;
        }

 /// <summary>
 /// Lấy dữ liệu từ câu lệnh chứa trong thuộc tính Command
 /// </summary>
 /// <returns></returns>
 private DataSet getData() //Get data with SQLcommand
 {
     Connect();
     trans = conn.BeginTransaction();
     DataSet ds = new DataSet();
     cmd.Connection = conn;
     cmd.CommandText = Command;
     cmd.CommandType = Commandtype;
     cmd.Transaction = trans;
     NpgsqlDataAdapter adapter = new NpgsqlDataAdapter(cmd);
     try
     {
         adapter.Fill(ds);
         trans.Commit();
         Disconnect();
         return ds;
     }
     catch (NpgsqlException ex)
     {
         Error = ex.Message;
         trans.Rollback();
     }
     return null;
 }