Question

I am looking for suggestions on how to handle a csv file that is being created, then uploaded by our customers, and that may have a comma in a value, like a company name.

Some of the ideas we are looking at are: quoted Identifiers (value ‘,’ values ‘,’etc) or using a | instead of a comma. The biggest problem is that we have to make it easy, or the customer won’t do it.

Answer 1

As others have said, you need to escape values that include quotes. Here’s a little CSV reader in C♯ that supports quoted values, including embedded quotes and carriage returns.

By the way, this is unit-tested code. I’m posting it now because this question seems to come up a lot and others may not want an entire library when simple CSV support will do.

You can use it as follows:

using System; public class test {     public static void Main()     {         using ( CsvReader reader = new CsvReader( 'data.csv' ) )         {             foreach( string[] values in reader.RowEnumerator )             {                 Console.WriteLine( 'Row {0} has {1} values.', reader.RowIndex, values.Length );             }         }         Console.ReadLine();     } } 

Here are the classes. Note that you can use the Csv.Escape function to write valid CSV as well.

using System.IO; using System.Text.RegularExpressions;  public sealed class CsvReader : System.IDisposable {     public CsvReader( string fileName ) : this( new FileStream( fileName, FileMode.Open, FileAccess.Read ) )     {     }      public CsvReader( Stream stream )     {         __reader = new StreamReader( stream );     }      public System.Collections.IEnumerable RowEnumerator     {         get {             if ( null == __reader )                 throw new System.ApplicationException( 'I can't start reading without CSV input.' );              __rowno = 0;             string sLine;             string sNextLine;              while ( null != ( sLine = __reader.ReadLine() ) )             {                 while ( rexRunOnLine.IsMatch( sLine ) && null != ( sNextLine = __reader.ReadLine() ) )                     sLine += '\n' + sNextLine;                  __rowno++;                 string[] values = rexCsvSplitter.Split( sLine );                  for ( int i = 0; i < values.Length; i++ )                     values[i] = Csv.Unescape( values[i] );                  yield return values;             }              __reader.Close();         }     }      public long RowIndex { get { return __rowno; } }      public void Dispose()     {         if ( null != __reader ) __reader.Dispose();     }      //============================================       private long __rowno = 0;     private TextReader __reader;     private static Regex rexCsvSplitter = new Regex( @',(?=(?:[^'']*''[^'']*'')*(?![^'']*''))' );     private static Regex rexRunOnLine = new Regex( @'^[^'']*(?:''[^'']*''[^'']*)*''[^'']*$' ); }  public static class Csv {     public static string Escape( string s )     {         if ( s.Contains( QUOTE ) )             s = s.Replace( QUOTE, ESCAPED_QUOTE );          if ( s.IndexOfAny( CHARACTERS_THAT_MUST_BE_QUOTED ) > -1 )             s = QUOTE + s + QUOTE;          return s;     }      public static string Unescape( string s )     {         if ( s.StartsWith( QUOTE ) && s.EndsWith( QUOTE ) )         {             s = s.Substring( 1, s.Length - 2 );              if ( s.Contains( ESCAPED_QUOTE ) )                 s = s.Replace( ESCAPED_QUOTE, QUOTE );         }          return s;     }       private const string QUOTE = '\'';     private const string ESCAPED_QUOTE = '\'\'';     private static char[] CHARACTERS_THAT_MUST_BE_QUOTED = { ',', ''', '\n' }; }