Year,Make,Model,Description,Price
1997,Ford,"E350
F150","ac, abs,
moon",3000.00
1999,Chevy,"Venture ""Extended Edition""","",4900.00
1999,Chevy,"Venture ""Extended Edition, Very Large""",,5000.00
1996,Jeep,Grand Cherokee,"MUST SELL!
air,
"",moon,""
roof, loaded",4799.00
1999,BMW,Z3,"used",14900.00
1999, Toyota,Corolla,,7000.00

如您所见，有些行是多行的，包含引号和逗号，这将给出下表：

public class car
{// you can use fields or propertiespublic string Year;public string Make;public string Model;public string Description;public string Price;
}// listcars = List<car>
var listcars = fastCSV.ReadFile<cars>("csvstandard.csv", // filenametrue,              // has header',',               // delimiter(o, c) =>          // to object function o : car object, c : columns array read{o.Year = c[0];o.Make = c[1];o.Model = c[2];o.Description = c[3];o.Price = c[4];// add to listreturn true;});fastCSV.WriteFile<LocalWeatherData>("filename2.csv",   // filenamenew string[] { "WBAN", "Date", "SkyCondition" }, // headers defined or null'|',               // delimiterlist,              // list of LocalWeatherData to save(o, c) =>          // from object function {c.Add(o.WBAN);c.Add(o.Date.ToString("yyyyMMdd"));c.Add(o.SkyCondition);});

助手函数以提高性能

public class LocalWeatherData
{public string WBAN;public DateTime Date;public string SkyCondition;
}var list = fastCSV.ReadFile<LocalWeatherData>("201503hourly.txt", true, ',', (o, c) =>{bool add = true;o.WBAN = c[0];// c[1] data is in "20150301" formato.Date = new DateTime(fastCSV.ToInt(c[1], 0, 4), fastCSV.ToInt(c[1], 4, 2), fastCSV.ToInt(c[1], 6, 2));o.SkyCondition = c[4];//if (o.Date.Day % 2 == 0)//    add = false;return add;});

使用场景

var c = ParseLine(line, delimiter, cols);
T o = new T();
var b = mapper(o, c);
if (b)list.Add(o);

现在，CSV标准复杂性来自正确处理多行，这是通过计算一行中引号是否为奇数来完成的，因此，它是多行并读取行直到引号是偶数，这是在ReadFile()函数中完成的。

public static List<T> ReadFile<T>(string filename, bool hasheader, char delimiter, ToOBJ<T> mapper) where T : new()
{string[] cols = null;List<T> list = new List<T>();int linenum = -1;StringBuilder sb = new StringBuilder();bool insb = false;foreach (var line in File.ReadLines(filename)){try{linenum++;if (linenum == 0){if (hasheader){// actual col countint cc = CountOccurence(line, delimiter);if (cc == 0)throw new Exception("File does not have '" + delimiter + "' as a delimiter");cols = new string[cc + 1];continue;}elsecols = new string[_COLCOUNT];}var qc = CountOccurence(line, '\"');bool multiline = qc % 2 == 1 || insb;string cline = line;// if multiline add line to sb and continueif (multiline){insb = true;sb.Append(line);var s = sb.ToString();qc = CountOccurence(s, '\"');if (qc % 2 == 1){sb.AppendLine();continue;}cline = s;sb.Clear();insb = false;}var c = ParseLine(cline, delimiter, cols);T o = new T();var b = mapper(o, c);if (b)list.Add(o);}catch (Exception ex){throw new Exception("error on line " + linenum, ex);}}return list;
}private unsafe static int CountOccurence(string text, char c)
{int count = 0;int len = text.Length;int index = -1;fixed (char* s = text){while (index++ < len){char ch = *(s + index);if (ch == c)count++;}}return count;
}private unsafe static string[] ParseLine(string line, char delimiter, string[] columns)
{//return line.Split(delimiter);int col = 0;int linelen = line.Length;int index = 0;fixed (char* l = line){while (index < linelen){if (*(l + index) != '\"'){// non quotedvar next = line.IndexOf(delimiter, index);if (next < 0){columns[col++] = new string(l, index, linelen - index);break;}columns[col++] = new string(l, index, next - index);index = next + 1;}else{// quoted string change "" -> "int qc = 1;int start = index;char c = *(l + ++index);// find matching quote until delim or EOLwhile (index++ < linelen){if (c == '\"')qc++;if (c == delimiter && qc % 2 == 0)break;c = *(l + index);}columns[col++] = new string(l, start + 1, index - start - 3).Replace("\"\"", "\"");}}}return columns;
}

ParseLine()负责以一种优化的unsafe方式从一行中提取列。

public static void WriteFile<T>(string filename, string[] headers, char delimiter, List<T> list, FromObj<T> mapper)
{using (FileStream f = new FileStream(filename, FileMode.Create, FileAccess.Write)){using (StreamWriter s = new StreamWriter(f)){if (headers != null)s.WriteLine(string.Join(delimiter.ToString(), headers));foreach (var o in list){List<object> cols = new List<object>();mapper(o, cols);for (int i = 0; i < cols.Count; i++){// qoute string if needed -> \" \r \n delim var str = cols[i].ToString();bool quote = false;if (str.IndexOf('\"') >= 0){quote = true;str = str.Replace("\"", "\"\"");}if (quote == false && str.IndexOf('\n') >= 0)quote = true;if (quote == false && str.IndexOf('\r') >= 0)quote = true;if (quote == false && str.IndexOf(delimiter) >= 0)quote = true;if (quote)s.Write("\"");s.Write(str);if (quote)s.Write("\"");if (i < cols.Count - 1)s.Write(delimiter);}s.WriteLine();}s.Flush();}f.Close();}
}

样例用例

var testing = new List<LocalWeatherData>();
int line = 0;
var training = fastCSV.ReadFile<LocalWeatherData>("201503hourly.txt", true, ',', (o, c) =>{bool add = true;line++;o.Date = new DateTime(fastCSV.ToInt(c[1], 0, 4),fastCSV.ToInt(c[1], 4, 2),fastCSV.ToInt(c[1], 6, 2));o.SkyCondition = c[4];if (line % 3 == 0){add = false;test.Add(o);}return add;});