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客户定期出现“不支持嵌套/并发事务”。错误。在我这边不可重复，但试图了解它是如何发生的。它只发生在以下方法中：

public DataTable ExecuteDataTable(CommandType type, string query, params NpgsqlParameter[] parameters)
        {
            NpgsqlCommand command = PrepareCommand(type, query, parameters);

            // Use transaction for functions with refcursors. This is necessary to prevent cursors 
            // returned by refcursor function from closing after the implicity transaction is finished 
            // (just after we do the function call).
            NpgsqlTransaction t = sqlConnection.BeginTransaction();

            try
            {
                NpgsqlDataAdapter da = new NpgsqlDataAdapter(command);
                System.Data.DataSet ds = new System.Data.DataSet();

                // Fill the DataSet using default values for DataTable names, etc
                da.Fill(ds);
                t.Commit();

                // Detach the SqlParameters from the command object, so they can be used again
                command.Parameters.Clear();

                return ds.Tables[0];
            }
            catch (Exception e)
            {
                // Commit all transactions so connection can be used again (Npgsql does not allow nested transactions)
                t.Rollback();
                // Log error and problem query
                LogError(e);
                // Throw same exception to a higher level for correct handling
                throw e;
            }
        }

如果出现错误，我总是尝试回滚以避免嵌套事务，但是它会在某些安装中定期发生。是 Npgsql 问题还是实现中的问题？这怎么可能发生？如果 2 个进程同时从不同的类、应用程序运行此方法，这是否与连接池有关？

调用堆栈：

2013-10-08 13:00:27.6038|Common.Logging.NLog.NLogLogger.WriteInternal|Info|Job DEFAULT.SQLServerSyncScheduledJob 抛出 JobExecutionException：|System.InvalidOperationException：不支持嵌套/并发事务。在 Npgsql.NpgsqlConnection.BeginTransaction(IsolationLevel 级别) 在 Npgsql.NpgsqlConnection.BeginTransaction() 在 DbFramework.PgDataAccess.ExecuteDataTable(CommandType 类型，字符串查询，NpgsqlParameter[] 参数)

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