读写CSV文件，写txt

            var allFiles = Directory.GetFiles(@"D:\uploadpdf", "*.csv");
            string dataIsNull = @"D:\dataisnull.txt";
            string matchLog = @"D:\matchLog.txt";
            foreach (var filePath in allFiles)
            {
                DataTable dt = new DataTable();
                FileStream fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read);
                StreamReader streamReader = new StreamReader(fileStream);
                //记录每次读取的一行记录
                string strLine = string.Empty;
                //记录每行记录中的各字段的内容
                string[] aryLine = null;
                string[] tableHead = null;
                //标示列数
                int columCount = 0;
                //标示是否是读取的第一行
                bool isFirst = true;
                Console.Out.WriteLine("");
                StringBuilder headBuilder = new StringBuilder();
                //逐行读取CSV中的数据
                while ((strLine = streamReader.ReadLine()) != null)
                {
                    if (isFirst)
                    {
                        tableHead = strLine.Split(',');
                        isFirst = false;
                        columCount = tableHead.Length;
                        //创建列
                        foreach (var head in tableHead)
                        {
                            DataColumn column = new DataColumn(head);
                            dt.Columns.Add(column);
                            headBuilder.AppendFormat("{0}\t\t\t", head);
                        }
                        if (headBuilder.Length != 0)
                        {
                            using (StreamWriter sw = File.AppendText(matchLog))
                            {
                                sw.WriteLine(headBuilder.ToString());
                            }
                        }
                    }
                    else
                    {
                        aryLine = strLine.Split(',');
                        DataRow row = dt.NewRow();
                        if (aryLine.Length == columCount)
                        {
                            for (int i = 0; i < columCount; i++)
                            {
                                row[i] = aryLine[i];
                            }
                        }
                        dt.Rows.Add(row);
                    }
                }
                if (aryLine != null && aryLine.Length > 0)
                {
                    dt.DefaultView.Sort = tableHead[0] + " asc";
                }
                streamReader.Close();
                fileStream.Close();
                if (dt.Rows.Count == 0)
                {
                    //OutputLog(dataIsNull, string.Format("{0} data is null.", filePath));
                    continue;
                }
                StringBuilder mpAttributesLog = new StringBuilder();

                foreach (DataRow row in dt.Rows)
                {
                    //var values = row.ItemArray;
                    //foreach (var head in tableHead)
                    //{
                    //    mpAttributesLog.AppendFormat("{0}\t\t\t", row[head]);
                    //}
                    mpAttributesLog.Append(string.Join("\t\t\t", row.ItemArray));
                    if (mpAttributesLog.Length != 0)
                    {
                        using (StreamWriter sw = File.AppendText(matchLog))
                        {
                            sw.WriteLine(mpAttributesLog.ToString());
                            mpAttributesLog.Clear();
                        }
                    }
                }
            }