How to split csv whose columns may contain

Question

Given 2 1016 7 31 2008 14 22 Geoff Dalgas 6 5 2011 22 21 http   stackoverflow com  quot Corvallis  OR quot  7679 351 81 b437f461b3fd27387c5d8ab47a293d35 34 How to use C  to split the above information into strings as follows  2 1016 7 31 2008 14 22 Geoff Dalgas 6 5 2011 22 21 http   stackoverflow com Corvallis  OR 7679 351 81 b437f461b3fd27387c5d8ab47a293d35 34  As you can see one of the column contains    lt    Corvallis  OR  update Based on C  Regex Split - commas outside quotes string   result   Regex Split samplestring   quot            quot     quot     quot     quot       quot      quot

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It is so much late but this can be helpful for someone  We can use RegEx as bellow   Regex CSVParser   new Regex                                            String   Fields   CSVParser Split Test

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Use the Microsoft VisualBasic FileIO TextFieldParser class  This will handle parsing a delimited file  TextReader or Stream where some fields are enclosed in quotes and some are not    For example   using Microsoft VisualBasic FileIO   string csv    2 1016 7 31 2008 14 22 Geoff Dalgas 6 5 2011 22 21 http   stackoverflow com   Corvallis  OR   7679 351 81 b437f461b3fd27387c5d8ab47a293d35 34    TextFieldParser parser   new TextFieldParser new StringReader csv        You can also read from a file    TextFieldParser parser   new TextFieldParser  mycsvfile csv     parser HasFieldsEnclosedInQuotes   true  parser SetDelimiters        string   fields   while   parser EndOfData        fields   parser ReadFields        foreach  string field in fields                Console WriteLine field             parser Close      This should result in the following output    2 1016 7 31 2008 14 22 Geoff Dalgas 6 5 2011 22 21 http   stackoverflow com Corvallis  OR 7679 351 81 b437f461b3fd27387c5d8ab47a293d35 34   See Microsoft VisualBasic FileIO TextFieldParser for more information   You need to add a reference to Microsoft VisualBasic in the Add References  NET tab

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You could split on all commas that do have an even number of quotes following them   You would also like to view at the specf for CSV format about handling comma s   Useful Link   C  Regex Split - commas outside quotes

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Use a library like LumenWorks to do your CSV reading  It ll handle fields with quotes in them and will likely overall be more robust than your custom solution by virtue of having been around for a long time

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I see that if you paste csv delimited text in Excel and do a  Text to Columns   it asks you for a  text qualifier   It s defaulted to a double quote so that it treats text within double quotes as literal  I imagine that Excel implements this by going one character at a time  if it encounters a  text qualifier   it keeps going to the next  qualifier   You can probably implement this yourself with a for loop and a boolean to denote if you re inside literal text   public string   CsvParser string csvText        List lt string gt  tokens   new List lt string gt          int last   -1      int current   0      bool inText   false       while current  lt  csvText Length                switch csvText current                         case                      inText    inText  break              case                      if   inText                                         tokens Add csvText Substring last   1   current - last   Trim                                  last   current                                    break              default                  break                    current               if  last    csvText Length - 1                 tokens Add csvText Substring last 1  Trim                return tokens ToArray

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I had a problem with a CSV that contains fields with a quote character in them  so using the TextFieldParser  I came up with the following   private static string   parseCSVLine string csvLine      using  TextFieldParser TFP   new TextFieldParser new MemoryStream Encoding UTF8 GetBytes csvLine             TFP HasFieldsEnclosedInQuotes   true      TFP SetDelimiters            try                         return TFP ReadFields              catch  MalformedLineException              StringBuilder m sbLine   new StringBuilder           for  int i   0  i  lt  TFP ErrorLine Length  i                    if  i  gt  0  amp  amp  TFP ErrorLine i         amp  amp  TFP ErrorLine i   1          amp  amp  TFP ErrorLine i - 1                     m sbLine Append                  else           m sbLine Append TFP ErrorLine i                   return parseCSVLine m sbLine ToString                   A StreamReader is still used to read the CSV line by line  as follows   using StreamReader SR   new StreamReader FileName       while  SR Peek    gt -1      myStringArray   parseCSVLine SR ReadLine

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With Cinchoo ETL - an open source library  it can automatically handles columns values containing separators   string csv     2 1016 7 31 2008 14 22 Geoff Dalgas 6 5 2011 22 21 http   stackoverflow com   Corvallis  OR   7679 351 81 b437f461b3fd27387c5d8ab47a293d35 34    using  var p   ChoCSVReader LoadText csv              Console WriteLine p Dump         Output   Key  Column1  Type  String  Value  2 Key  Column2  Type  String  Value  1016 Key  Column3  Type  String  Value  7 31 2008 14 22 Key  Column4  Type  String  Value  Geoff Dalgas Key  Column5  Type  String  Value  6 5 2011 22 21 Key  Column6  Type  String  Value  http   stackoverflow com Key  Column7  Type  String  Value  Corvallis  OR Key  Column8  Type  String  Value  7679 Key  Column9  Type  String  Value  351 Key  Column10  Type  String  Value  81 Key  Column11  Type  String  Value  b437f461b3fd27387c5d8ab47a293d35 Key  Column12  Type  String  Value  34   For more information  please visit codeproject article   Hope it helps

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It is a tricky matter to parse  csv files when the  csv file could be either comma separated strings  comma separated quoted strings  or a chaotic combination of the two   The solution I came up with allows for any of the three possibilities   I created a method  ParseCsvRow   which returns an array from a csv string   I first deal with double quotes in the string by splitting the string on double quotes into an array called quotesArray   Quoted string  csv files are only valid if there is an even number of double quotes   Double quotes in a column value should be replaced with a pair of double quotes  This is Excel s approach    As long as the  csv file meets these requirements  you can expect the delimiter commas to appear only outside of pairs of double quotes   Commas inside of pairs of double quotes are part of the column value and should be ignored when splitting the  csv into an array     My method will test for commas outside of double quote pairs by looking only at even indexes of the quotesArray   It also removes double quotes from the start and end of column values       public static string   ParseCsvRow string csvrow                const string obscureCharacter                if  csvrow Contains obscureCharacter   throw new Exception  Error  csv row may not contain the     obscureCharacter     character             var unicodeSeparatedString                var quotesArray   csvrow Split           Split string on double quote character         if  quotesArray Length  gt  1                        for  var i   0  i  lt  quotesArray Length  i                                     CSV must use double quotes to represent a quote inside a quoted cell                    Quotes must be paired up                    Test if a comma lays outside a pair of quotes   If so  replace the comma with an obscure unicode character                 if  Math Round Math Round  decimal  i 2  2     i                                        var s   quotesArray i  Trim                        switch  s                                                case                                  quotesArray i    obscureCharacter      Change quoted comma seperated string to quoted  obscure character  seperated string                             break                                                             Build string and Replace quotes where quotes were expected                  unicodeSeparatedString     i  gt  0                quotesArray i  Trim                                    else                          String does not have any pairs of double quotes   It should be safe to just replace the commas with the obscure character             unicodeSeparatedString   csvrow Replace      obscureCharacter                      var csvRowArray   unicodeSeparatedString Split obscureCharacter 0              for  var i   0  i  lt  csvRowArray Length  i                          var s   csvRowArray i  Trim                if  s StartsWith        amp  amp  s EndsWith                                      csvRowArray i    s Length  gt  2   s Substring 1  s Length - 2            Remove start and end quotes                                   return csvRowArray          One downside of my approach is the way I temporarily replace delimiter commas with an obscure unicode character   This character needs to be so obscure  it would never show up in your  csv file   You may want to put more handling around this

[c#] How to split csv whose columns may contain ,

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