Extract comma separated portion of string with a RegEx in C#

Question

Sample data: !!Part|123456,ABCDEF,ABC132!!

The comma delimited list can be any number of any combination of alphas and numbers

I want a regex to match the entries in the comma separated list:

What I have is: !!PART\|(\w+)(?:,{1}(\w+))*!!

Which seems to do the job, the thing is I want to retrieve them in order into an ArrayList or similar so in the sample data I would want:

1 - 132456
2 - ABCDEF
3 - ABC123

The code I have is:

string partRegularExpression = @"!!PART\|(\w+)(?:,{1}(\w+))*!!"
Match match = Regex.Match(tag, partRegularExpression);
ArrayList results = new ArrayList();

foreach (Group group in match.Groups)
{
    results.Add(group.Value);
}

But that's giving me unexpected results. What am I missing?

Thanks

Edit: A solution would be to use a regex like !!PART\|(\w+(?:,??\w+)*)!! to capture the comma separated list and then split that as suggested by Marc Gravell

I am still curious for a working regex for this however :o)

Will your data always look similar to this? A need for regex is not immediately evident here. You could potentially parse off the exclamation points, split by the "|" and then split once more by comma to give you an array immediately. — cLFlaVA
– cLFlaVA, Commented Dec 15, 2008 at 13:40
Are you sure that you want to use a RegEx? "Some people, when confronted with a problem, think 'I know, I'll use regular expressions.' Now they have two problems." — Christoffer Lette
– Christoffer Lette, Commented Dec 15, 2008 at 13:41
Nice quote. :o) I'm doing a number of (admittidly simpler) tags with Regex and there fine, so when I hit this one I continued down that route. — NikolaiDante
– NikolaiDante, Commented Dec 15, 2008 at 13:47
Data would be similar, the start and end would be the same the comma seperated list could have one to x entries. — NikolaiDante
– NikolaiDante, Commented Dec 15, 2008 at 13:48

ICR · Accepted Answer · 2008-12-15 13:57:29Z

3

You can either use split:

string csv = tag.Substring(7, tag.Length - 9);
string[] values = csv.Split(new char[] { ',' });

Or a regex:

Regex csvRegex = new Regex(@"!!Part\|(?:(?<value>\w+),?)+!!");
List<string> valuesRegex = new List<string>();
foreach (Capture capture in csvRegex.Match(tag).Groups["value"].Captures)
{
    valuesRegex.Add(capture.Value);
}

answered Dec 15, 2008 at 13:57

ICR

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4 Comments

NikolaiDante Over a year ago

Just threw my unit tests against this and it passed them all. Thanks :o)

Martin Brown Over a year ago

It is interesting to see that this regex solution is slightly faster than mine. As usual though, the split version is fastest of all.

Martin Brown Over a year ago

On 1 million iterations I’m getting 0.54sec for my RegEx 0.44sec for this one and 0.10sec for the split. Both RegEx’s are compiled.

ICR Over a year ago

For one thing your regex is using a non-greedy wildcard match, which requires quite a bit of backtracking.

Marc Gravell · Accepted Answer · 2008-12-15 13:41:13Z

1

Unless I'm mistaken, that still only counts as one group. I'm guessing you'll need to do a string.Split(',') to do what you want? Indeed, it looks a lot simpler to not bother with regex at all here... Depending on the data, how about:

        if (tag.StartsWith("!!Part|") && tag.EndsWith("!!"))
        {
            tag = tag.Substring(7, tag.Length - 9);
            string[] data = tag.Split(',');
        }

answered Dec 15, 2008 at 13:41

Marc Gravell

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2 Comments

NikolaiDante Over a year ago

The (?: ) bracket isn't captured, only the group (\w+) inside. But no reason it couldn't be. I guess I'm over complicating things going 100% regex.

NikolaiDante Over a year ago

A regex of the form: !!PART\|(\w+(?:,??\w+)*)!! seems to capture only the comma seperated list. I could then split the single group (if needed).

Martin Brown · Accepted Answer · 2008-12-15 14:10:32Z

1

I think the RegEx you are looking for is this:

(?:^!!PART\|){0,1}(?<value>.*?)(?:,|!!$)

This can then be run like this

        string tag = "!!Part|123456,ABCDEF,ABC132!!";

        string partRegularExpression = @"(?:^!!PART\|){0,1}(?<value>.*?)(?:,|!!$)";
        ArrayList results = new ArrayList();

        Regex extractNumber = new Regex(partRegularExpression, RegexOptions.IgnoreCase);
        MatchCollection matches = extractNumber.Matches(tag);
        foreach (Match match in matches)
        {
            results.Add(match.Groups["value"].Value);
        }            

        foreach (string s in results)
        {
            Console.WriteLine(s);
        }

edited Dec 15, 2008 at 14:10

answered Dec 15, 2008 at 13:54

Martin Brown

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2 Comments

NikolaiDante Over a year ago

Failed the case !!PART|123456!! In the array list I had two entries "!!" and """"

Martin Brown Over a year ago

You need to run this slightly differently, see the example code I've added.

ZombieSheep · Accepted Answer · 2008-12-15 13:53:25Z

0

The following code

string testString = "!!Part|123456,ABCDEF,ABC132!!";
foreach(string component in testString.Split("|!,".ToCharArray(),StringSplitOptions.RemoveEmptyEntries) )
{
    Console.WriteLine(component);
}

will give the following output

Part
123456
ABCDEF
ABC132

This has the advantage of making the comma separated part of the string match up with the index numbers you (possibly accidentally incorrectly) specified in the original question (1,2,3).

HTH

-EDIT- forgot to mention, this may have drawbacks if the format of each string is not as expected above, but then again it would break just as easily without stupendously complex regex too.

answered Dec 15, 2008 at 13:53

ZombieSheep

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2 Comments

NikolaiDante Over a year ago

yeah should have been 0,1,2. D'oh! :o)

NikolaiDante Over a year ago

i have a seperate validating regex for the tag, so by the time I get to extracting the data it would have been validated, but thanks for the heads up! :o)

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