working with regex and csv quoted strings

Question

i am trying to convert a string like

"test",645,23.4,42,"13,13,14","test"

into

"test","645","23.4","42","13,13,14","test"

i am trying with this code.

string pattern = "\",(? !\")";
string pattern2 = "(?<!\"),(? !\")";
string pattern3 = "(?<!\"),\"";
string replacement = "\",\"";

Regex rgx = new Regex(pattern);
catalogo = rgx.Replace(catalogo, replacement);
rgx = new Regex(pattern2);
catalogo = rgx.Replace(catalogo, replacement);
rgx = new Regex(pattern3);
catalogo = rgx.Replace(catalogo, replacement);

but i dont know how to get past the value that already contains commas. "13,13,14" since it will change it into "13","13","14"

i dont know if thats the best way to convert the string, but at least i believe that it will do the job, just that i dont know why i get past this.

@Steve i dont know what that is, ill look for it, but if you are kind to give me your thoughts on how i could use that i would be gratefull — pato.llaguno
– pato.llaguno, Commented Oct 7, 2015 at 22:46
my file is being retrieved from a FTP server, and im trying to get that info into a datatable — pato.llaguno
– pato.llaguno, Commented Oct 7, 2015 at 22:47
I have been using codeproject.com/Articles/9258/A-Fast-CSV-Reader for years. Simple, easy to use. — Eric J.
– Eric J., Commented Oct 7, 2015 at 22:48
I definitely recommend TextFieldParser - it's part of the .NET framework and it works well. I've used it several times (all from C# apps). — Tim
– Tim, Commented Oct 7, 2015 at 23:01

Steve · Accepted Answer · 2015-10-07 23:11:23Z

4

I am not sure why you need to use a Regex to parse comma separated data.
There are a lot of free libraries specialized in parsing this kind of data and the same NET Framework provides a specific class in the Microsoft.VisualBasic.IO namespace

Here how you could use it

string t = "\"test\",645,23.4,42,\"13,13,14\",\"test\"";
StringReader sr = new StringReader(t);
TextFieldParser tp = new TextFieldParser(sr);
tp.Delimiters = new string[] {","};
tp.HasFieldsEnclosedInQuotes = true;

string[] result = tp.ReadFields();

foreach(string s in result)
   Console.WriteLine(s);

This code retrieves your data and respect the fields enclosed in double quotes avoiding to parse the content of these fields. However it seems that you want also a double quote arounde each string retrieved so you need a second loop to readd the missing quotes

for(int x = 0; x < result.Length; x++)
    result[x] = string.Concat("\"", result[x], "\"");

By the way, I am not recommending to use this class, free libraries or custom code. To choice between these options is always a tradeoff between costs (write, debug, test, document) and perfomances. If performance is a critical aspect of your solution then you need to test a lot of things using the real data coming from your FTP server. A task that only you could perform.

edited Oct 7, 2015 at 23:11

answered Oct 7, 2015 at 22:48

Steve

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8 Comments

pato.llaguno Over a year ago

i cant use TextFieldParser, i get an error trying to import using Microsoft.VisualBasic.FileIO; i am doing a c# console app.

Steve Over a year ago

This is strange because I have tested this code in a Console application. What error do you get?

Tim Over a year ago

I've used TextFieldParser in several C# applications - there shouldn't be any issue with it. Did you add a reference to Microsoft.VisualBasic.FileIO in your project?

Steve Over a year ago

It would be an act of courtesy (not just for me but also for the Readers) to explain the downvote.

Tim Over a year ago

That has to be the most non-sensical downvote I've seen in my time on this site.....

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