Regex to remove multiple consecutive commas and replace with single comma

Question

Given the input string "Test,,test,,,test,test"

and using the following C# snippet I would have expected the duplicate commas to be replaced by a single comma and results in...

"Test,test,test,test"

private static string TruncateCommas(string input)
{
    return Regex.Replace(input, @",+", ",");
}

But what I am seeing is "Test,,test,,,test,test" as the output from this function.

Do I need to escape the comma in the regex? Or should this regex be working.

Wild guess: You're not looking at the return value from that method. — Joey, Sep 08 '17 at 14:47
@itsme86: `@",{2,}"` is *more readable* and (at least potentially) more effcient: we don't touch *single* commas — Dmitry Bychenko, Sep 08 '17 at 14:52
"But what I am seeing is.." please post the way that you test the function. The error is there — Mong Zhu, Sep 08 '17 at 14:56
I had a spaces between the commas. I've ammended my Regex and now all is happy. Regex.Replace(concatenatedString, @"(,\s)+", @"$1"); — Nattrass, Sep 09 '17 at 09:23

score 2 · Accepted Answer · answered Sep 08 '17 at 14:59

2

Do I need to escape the comma in the regex?

No.

Or should this regex be working.

Yes.

Please construct your test the following way:

void Main()
{
    string s = "Test,,test,,,test,test";

    string result = TruncateCommas(s);

    Console.WriteLine(result);
}

Output

Test,test,test,test

answered Sep 08 '17 at 14:59

Mong Zhu

1

Thankyou for making me think about this correctly. It was indeed the input. string.Format("{0}, {1}, {2}, {3}, {4}, {5}, {6}", ...). There was a space in between the commas on my input! – Nattrass Sep 09 '17 at 09:17
@Nattrass your welcome, glad to hear that you solved your problem. Good fortune – Mong Zhu Sep 11 '17 at 06:14

1 Answers1