CsvWriter

using System;
using System.Collections.Generic;
using System.Data;
using System.IO;
using System.Linq;
using System.Text;

namespace BrowsePearls.CSV
{
    public sealed class CsvWriter : IDisposable
    {

        #region Members
        private StreamWriter _streamWriter;
        private bool _replaceCarriageReturnsAndLineFeedsFromFieldValues = true;
        private string _carriageReturnAndLineFeedReplacement = ",";

        private bool _dispose = false;
        #endregion Members

        #region Properties

        /// <summary>
        /// CSVRecord的字段中如果有"\r","\r\n","\n"时,决定是否被替换成其他字符.
        /// 为什么要替换呢?因为字段会被拼接成CSV格式的字符串写入磁盘,字段的换行符
        /// 会导致换行,中断一条完整的记录.
        /// </summary>
        public bool ReplaceCarriageReturnsAndLineFeedsFromFieldValues
        {
            get
            {
                return _replaceCarriageReturnsAndLineFeedsFromFieldValues;
            }
            set
            {
                _replaceCarriageReturnsAndLineFeedsFromFieldValues = value;
            }
        }
        /// <summary>
        /// 替换CSVRecord的字段中的"\r","\r\n","\n"的字符.
        /// 我们加载时,可以解析该字符,替换成换行符.
        /// </summary>
        public string CarriageReturnAndLineFeedReplacement
        {
            get
            {
                return _carriageReturnAndLineFeedReplacement;   
            }
            set
            {
                _carriageReturnAndLineFeedReplacement = value;
            }
        }

        #endregion Properties

        #region Methods

        #region CsvFile write methods
        public void WriteCsv(CsvFile csvFile, string filePath)
        {
            WriteCsv(csvFile, filePath, null);
        }


        public void WriteCsv(CsvFile csvFile, string filePath, Encoding encoding)
        {
            if (File.Exists(filePath))
                File.Delete(filePath);

            using (StreamWriter writer = new StreamWriter(filePath, false, encoding ?? Encoding.Default))
            {
                WriteToStream(csvFile, writer);
                writer.Flush();
                writer.Close();
            }
        }


        public void WriteCsv(CsvFile csvFile, Stream stream)
        {
            WriteCsv(csvFile, stream, null);
        }

        public void WriteCsv(CsvFile csvFile, Stream stream, Encoding encoding)
        {
            stream.Position = 0;
            _streamWriter = new StreamWriter(stream, encoding ?? Encoding.Default);
            WriteToStream(csvFile, _streamWriter);
            _streamWriter.Flush();
            stream.Position = 0;
        }

        public string WriteCsv(CsvFile csvFile, Encoding encoding)
        {
            string content = string.Empty;

            using (MemoryStream memoryStream = new MemoryStream())
            {
                using (StreamWriter writer = new StreamWriter(memoryStream, encoding ?? Encoding.Default))
                {
                    WriteToStream(csvFile, writer);
                    writer.Flush();
                    memoryStream.Position = 0;

                    using (StreamReader reader = new StreamReader(memoryStream, encoding ?? Encoding.Default))
                    {
                        content = reader.ReadToEnd();
                        writer.Close();
                        reader.Close();
                        memoryStream.Close();
                    }
                }
            }

            return content;
        }

        #endregion CsvFile write methods

        #region DataTable write methods


        public void WriteCsv(DataTable dataTable, string filePath)
        {
            WriteCsv(dataTable, filePath, null);
        }


        public void WriteCsv(DataTable dataTable, string filePath, Encoding encoding)
        {
            if (File.Exists(filePath))
                File.Delete(filePath);

            using (StreamWriter writer = new StreamWriter(filePath, false, encoding ?? Encoding.Default))
            {
                WriteToStream(dataTable, writer);
                writer.Flush();
                writer.Close();
            }
        }


        public void WriteCsv(DataTable dataTable, Stream stream)
        {
            WriteCsv(dataTable, stream, null);
        }


        public void WriteCsv(DataTable dataTable, Stream stream, Encoding encoding)
        {
            stream.Position = 0;
            _streamWriter = new StreamWriter(stream, encoding ?? Encoding.Default);
            WriteToStream(dataTable, _streamWriter);
            _streamWriter.Flush();
            stream.Position = 0;
        }


        public string WriteCsv(DataTable dataTable, Encoding encoding)
        {
            string content = string.Empty;

            using (MemoryStream memoryStream = new MemoryStream())
            {
                using (StreamWriter writer = new StreamWriter(memoryStream, encoding ?? Encoding.Default))
                {
                    WriteToStream(dataTable, writer);
                    writer.Flush();
                    memoryStream.Position = 0;

                    using (StreamReader reader = new StreamReader(memoryStream, encoding ?? Encoding.Default))
                    {
                        content = reader.ReadToEnd();
                        writer.Close();
                        reader.Close();
                        memoryStream.Close();
                    }
                }
            }

            return content;
        }

        #endregion DataTable write methods


        private void WriteToStream(CsvFile csvFile, TextWriter writer)
        {
            if (csvFile.Headers.Count > 0)
                WriteRecord(csvFile.Headers, writer);

            csvFile.Records.ForEach(record => WriteRecord(record.Fields, writer));
        }


        private void WriteToStream(DataTable dataTable, TextWriter writer)
        {
            List<string> fields = (from DataColumn column in dataTable.Columns select column.ColumnName).ToList();
            WriteRecord(fields, writer);

            foreach (DataRow row in dataTable.Rows)
            {
                fields.Clear();
                fields.AddRange(row.ItemArray.Select(o => o.ToString()));
                WriteRecord(fields, writer);
            }
        }


        private void WriteRecord(IList<string> fields, TextWriter writer)
        {
            for (int i = 0; i < fields.Count; i++)
            {
                bool quotesRequired = fields[i].Contains(",") || fields[i].Contains(" ");
                bool escapeQuotes = fields[i].Contains("\"");
                string fieldValue = (escapeQuotes ? fields[i].Replace("\"", "\"\"") : fields[i]);

                if(fieldValue == "")
                {
                    fieldValue = ",";
                }

                if (ReplaceCarriageReturnsAndLineFeedsFromFieldValues && (fieldValue.Contains("\r") || fieldValue.Contains("\n")))
                {
                    quotesRequired = true;
                    fieldValue = fieldValue.Replace("\r\n", CarriageReturnAndLineFeedReplacement);
                    fieldValue = fieldValue.Replace("\r", CarriageReturnAndLineFeedReplacement);
                    fieldValue = fieldValue.Replace("\n", CarriageReturnAndLineFeedReplacement);
                }

                string tmp = string.Format("{0}{1}{0}{2}",
                    (quotesRequired || escapeQuotes ? "\"" : string.Empty),
                    fieldValue,
                    (i < (fields.Count - 1) && fieldValue == "," ? "," : string.Empty));

                writer.Write(string.Format("{0}{1}{0}{2}", 
                    (quotesRequired || escapeQuotes ? "\"" : string.Empty),
                    fieldValue, 
                    ( i < (fields.Count - 1) && fieldValue != "," ? "," : string.Empty)));
            }

            writer.WriteLine();
        }


        public void Dispose()
        {
            if (!_dispose)
            {
                _dispose = true;
                CleanUp();
                GC.SuppressFinalize(this);
            }
        }

        ~CsvWriter()
        {
            CleanUp();
        }

        /// <summary>
        /// 释放非托管资源
        /// </summary>
        private void CleanUp()
        {
            if (_streamWriter == null) 
                return;

            _streamWriter.Close();
            _streamWriter.Dispose();
        }
        #endregion Methods
    }
}

CsvWriter

原文：https://www.cnblogs.com/browsepearls/p/13769546.html