using System;
using System.Collections.Generic;
using System.Data;
using System.IO;
using System.Text;
namespace BrowsePearls.CSV
{
/// <summary>
/// 从各种类型的数据源读取CSV格式的内容
/// </summary>
public sealed class CsvReader : IDisposable
{
#region Members
private FileStream _fileStream;
private Stream _stream;
private StreamReader _streamReader;
private StreamWriter _streamWriter;
private Stream _memoryStream;
private Encoding _encoding;
private readonly StringBuilder _columnBuilder = new StringBuilder(100);
private readonly Type _type = Type.File;
private bool _dispose = false;
#endregion Members
#region Properties
/// <summary>
/// 设置成true，会自动去除读到的字段的值两端的空格。 如 "hello world ",实际读到的是[hello world],而不是[hello world ].
/// </summary>
public bool TrimColumns { get; set; } = true;
/// <summary>
/// 指示CSV有无标题行,CSVReader的方法不使用此属性,该属性在CsvFile加载一个CSV文件时使用,用于辨别是否填充CSVFile的Headers属性
/// </summary>
public bool HasHeaderRow { get; set; }
/// <summary>
/// 返回当前正在被读取的行的所有字段的值的集合。初始值为null
/// </summary>
public List<string> Fields { get; private set; }
/// <summary>
/// 返回当前正在被读取的行的字段的数量。未读取时，为null
/// </summary>
public int? FieldCount
{
get
{
return (Fields != null ? Fields.Count : (int?)null);
}
}
#endregion Properties
#region Enums
/// <summary>
/// 数据源类型
/// </summary>
private enum Type
{
File,
Stream,
String
}
#endregion Enums
#region Constructors
/// <summary>
/// 文件
/// </summary>
/// <param name="filePath">File path</param>
public CsvReader(string filePath)
{
_type = Type.File;
Initialise(filePath, Encoding.Default);
}
/// <summary>
/// 文件
/// </summary>
/// <param name="filePath">File path</param>
/// <param name="encoding">Encoding</param>
public CsvReader(string filePath, Encoding encoding)
{
_type = Type.File;
Initialise(filePath, encoding);
}
/// <summary>
/// 流
/// </summary>
/// <param name="stream">Stream</param>
public CsvReader(Stream stream)
{
_type = Type.Stream;
Initialise(stream, Encoding.Default);
}
/// <summary>
/// 流
/// </summary>
/// <param name="stream">Stream</param>
/// <param name="encoding">Encoding</param>
public CsvReader(Stream stream, Encoding encoding)
{
_type = Type.Stream;
Initialise(stream, encoding);
}
/// <summary>
/// csv字符串
/// </summary>
/// <param name="encoding"></param>
/// <param name="csvContent"></param>
public CsvReader(Encoding encoding, string csvContent)
{
_type = Type.String;
Initialise(encoding, csvContent);
}
#endregion Constructors
#region Methods
/// <summary>
/// 文件
/// </summary>
/// <param name="filePath"></param>
/// <param name="encoding"></param>
private void Initialise(string filePath, Encoding encoding)
{
if (!File.Exists(filePath))
throw new FileNotFoundException(string.Format("The file ‘{0}‘ does not exist.", filePath));
_fileStream = File.OpenRead(filePath);
Initialise(_fileStream, encoding);
}
/// <summary>
/// 流
/// </summary>
/// <param name="stream"></param>
/// <param name="encoding"></param>
private void Initialise(Stream stream, Encoding encoding)
{
if (stream == null)
throw new ArgumentNullException("The supplied stream is null.");
_stream = stream;
_stream.Position = 0;
_encoding = (encoding ?? Encoding.Default);
_streamReader = new StreamReader(_stream, _encoding);
}
/// <summary>
/// csv字符串
/// </summary>
/// <param name="encoding"></param>
/// <param name="csvContent"></param>
private void Initialise(Encoding encoding, string csvContent)
{
if (csvContent == null)
throw new ArgumentNullException("The supplied csvContent is null.");
_encoding = (encoding ?? Encoding.Default);
_memoryStream = new MemoryStream(csvContent.Length);
_streamWriter = new StreamWriter(_memoryStream);
_streamWriter.Write(csvContent);
_streamWriter.Flush();
Initialise(_memoryStream, encoding);
}
/// <summary>
/// 读下一行记录
/// </summary>
/// <returns>如果成功读取一行记录，返回true，否则返回false</returns>
public bool ReadNextRecord()
{
Fields = null;
string line = _streamReader.ReadLine();
while(line != null && line.Replace(" ","").Length == 0)
{
line = _streamReader.ReadLine();
}
if (line == null)
return false;
ParseLine(line);
return true;
}
public DataTable ReadIntoDataTable()
{
return ReadIntoDataTable(new System.Type[] {});
}
/// <summary>
///
/// </summary>
/// <param name="columnTypes">列类型。如果提供类型数组长度小于标题数目，后面的标题默认是string</param>
/// <returns></returns>
public DataTable ReadIntoDataTable(System.Type[] columnTypes)
{
DataTable dataTable = new DataTable();
bool addedHeader = false;
_stream.Position = 0;
while (ReadNextRecord())
{
if (!addedHeader)
{
for (int i = 0; i < Fields.Count; i++)
dataTable.Columns.Add(Fields[i], (columnTypes.Length > i ? columnTypes[i] : typeof(string)));
addedHeader = true;
continue;
}
DataRow row = dataTable.NewRow();
for (int i = 0; i < Fields.Count; i++)
row[i] = Fields[i];
dataTable.Rows.Add(row);
}
return dataTable;
}
/// <summary>
/// 解析csv行
/// </summary>
/// <param name="line">Line</param>
private void ParseLine(string line)
{
Fields = new List<string>();
_columnBuilder.Remove(0, _columnBuilder.Length);
bool inColumn = false;
bool inQuotes = false;
int quoteCount = 0;
for (int i = 0; i < line.Length; ++i)
{
char character = line[i];
//未进入列
if (!inColumn)
{
//去除列前的所有空格
if (character == ‘ ‘)
{
continue;
}
//第一次遇到的非空白字符若是逗号，则认为该列值是空字符串
else if (character == ‘,‘)
{
Fields.Add(string.Empty);
inColumn = false;
inQuotes = false;
continue;
}
//第一次遇到的非空白字符若是双引号，则认为进入了列，且该列是必须用双引号括起来的特殊列
else if (character == ‘"‘)
{
inColumn = true;
inQuotes = true;
quoteCount++;
continue;
}
//其他字符则标记进入了列，但是是不需要用双引号括起来的普通列
else
{
inColumn = true;
inQuotes = false;
}
}
else // 进入列
{
//如果是被双引号包含的特殊列
if (inQuotes)
{
// 双引号计数器必定为奇数
if (quoteCount % 2 == 0)
{
throw new FormatException("Invalid double quotes");
}
//如果是一个列的最后一个双引号
if (character == ‘"‘ && (i + 1) < line.Length && line[i + 1] != ‘"‘)
{
quoteCount++;
//去除结束双引号与逗号之间的无效空白字符
for (int j = 1; ; ++j)
{
if ((i + j) < line.Length && line[i + j] == ‘,‘)
{
i = i + j;
inColumn = false;
break;
}
else if ((i + j) < line.Length && line[i + j] == ‘ ‘)
{
;//空语句
}
else if(i + j == line.Length)
{
i = i + j;
break;
}
}
}
//处理双引号。 列中的双引号必须成对且无间隔的出现
else if (character == ‘"‘ && (i + 1) < line.Length && line[i + 1] == ‘"‘)
{
++i;
quoteCount = quoteCount + 2;
}
else if(character == ‘"‘ && i + 1 == line.Length)
{
quoteCount++;
inColumn = false;
}
}
else //处理普通列
{
if (character == ‘,‘)
{
quoteCount = 0;
inColumn = false;
}
else if(character == ‘"‘)
{
throw new FormatException("This field can‘t contatin double quotes because there aren‘t double quotes at both ends of field");
}
}
}
if (!inColumn)
{
string field = inQuotes ? _columnBuilder.ToString() : _columnBuilder.ToString().Trim();
Fields.Add(TrimColumns ? field.Trim() : field);
_columnBuilder.Remove(0, _columnBuilder.Length);
inQuotes = false;
quoteCount = 0;
}
else
_columnBuilder.Append(character);
}
//处理最后一列
if (inColumn)
{
if (inQuotes)
{
if (quoteCount % 2 != 0)
{
throw new FormatException("Invalid double quotes");
}
}
else
{
if(quoteCount != 0)
{
throw new FormatException("Invalid double quotes");
}
}
Fields.Add(TrimColumns ? _columnBuilder.ToString().Trim() : _columnBuilder.ToString());
inColumn = false;
quoteCount = 0;
}
if(!inColumn && line.Trim().EndsWith(","))
{
Fields.Add(string.Empty);
}
}
public void Dispose()
{
if (!_dispose)
{
_dispose = true;
CleanUp();
GC.SuppressFinalize(this);
}
}
~CsvReader()
{
CleanUp();
}
/// <summary>
/// 释放非托管资源
/// </summary>
private void CleanUp()
{
if (_streamReader != null)
{
_streamReader.Close();
_streamReader.Dispose();
}
if (_streamWriter != null)
{
_streamWriter.Close();
_streamWriter.Dispose();
}
if (_memoryStream != null)
{
_memoryStream.Close();
_memoryStream.Dispose();
}
if (_fileStream != null)
{
_fileStream.Close();
_fileStream.Dispose();
}
if ((_type == Type.String || _type == Type.File) && _stream != null)
{
_stream.Close();
_stream.Dispose();
}
}
#endregion Methods
}
}
原文：https://www.cnblogs.com/browsepearls/p/13769540.html