split a comma-separated string with both quoted and unquoted strings.

Question

I have the following comma-separated string that I need to split. The problem is that some of the content is within quotes and contains commas that shouldnt be used in the split...

String:
111,222,"33,44,55",666,"77,88","99"

I want the output:
111
222
33,44,55
666
77,88
99

I have tried this:
(?:,?)((?<=")[^"]+(?=")|[^",]+)
But it reads the comma between "77,88","99" as a hit and I get the following output:
111
222
33,44,55
666
77,88
,
99

Can anybody help me? Im running out of hours... :) /Peter

Answer 1

Don't reinvent a CSV parser, try FileHelpers.

Answer 2

I have used this csv reader--it is fast!

Answer 3

Depending on your needs you may not be able to use a csv parser, and may in fact want to re-invent the wheel!!

You can do so with some simple regex

(?:^|,)(\"(?:[^\"]+|\"\")*\"|[^,]*)

This will do the following:

(?:^|,) = Match expression "Beginning of line or string ","

(\"(?:[^\"]+|\"\")\"|[^,]) = A numbered capture group, this will select between 2 alternatives:

1. stuff in quotes
2. stuff between commas

This should give you the output you are looking for.

Example code in C#

public void SplitCSV(string input)
{
    Regex csvSplit = new Regex("(?:^|,)(\"(?:[^\"]+|\"\")*\"|[^,]*)", RegexOptions.Compiled);

    foreach (Match match in csvSplit.Matches(input))
    {
        Console.WriteLine(match.Value.TrimStart(','));
    }
}

private void button1_Click(object sender, RoutedEventArgs e)
{
    SplitCSV("111,222,\"33,44,55\",666,\"77,88\",\"99\"");
}

Answer 4

Try this:

       string s = @"111,222,""33,44,55"",666,""77,88"",""99""";

       List<string> result = new List<string>();

       var splitted = s.Split('"').ToList<string>();
       splitted.RemoveAll(x => x == ",");
       foreach (var it in splitted)
       {
           if (it.StartsWith(",") || it.EndsWith(","))
           {
               var tmp = it.TrimEnd(',').TrimStart(',');
               result.AddRange(tmp.Split(','));
           }
           else
           {
               if(!string.IsNullOrEmpty(it)) result.Add(it);
           }
      }
       //Results:

       foreach (var it in result)
       {
           Console.WriteLine(it);
       }

Answer 5

I once had to do something similar and in the end I got stuck with Regular Expressions. The inability for Regex to have state makes it pretty tricky - I just ended up writing a simple little parser.

If you're doing CSV parsing you should just stick to using a CSV parser - don't reinvent the wheel.