Replace a character inside a string using C# Regex

Question

I would like to know how to replace , characters inside array brackets [] with another character, say .. The string expression I have is below:

Attributes["412324 - PENNDOT I-95", "Category"].Value, Attributes["412324 - PENNDOT I-95", "Category"].Code

The expected output should be:

Attributes["412324 - PENNDOT I-95". "Category"].Value, Attributes["412324 - PENNDOT I-95". "Category"].Code

Have you tried anything yet? Post some code of what you've attempted so far. — Darko
– Darko, Commented Apr 10, 2012 at 5:25

Jay · Accepted Answer · 2012-04-10 05:35:14Z

6

var regex = new Regex(@"(?<=\[[^\[\]]*),(?=[^\[\]]*\])");
return regex.Replace(<your sample string>, ".");

Within the regex pattern, to the left of the , is a positive lookbehind zero-width assertion that means there must be a [ and then zero or more characters that are neither [ nor ] leading up to the comma.

After the comma, a positive lookahead zero-width assertion that means there can be zero or more characters that are neither [ nor ] then there must be a closing ].

Zero-width assertions mean that the pattern must precede or follow the matched text, but are not part of the match. Since we are only matching the , our replacement is just the .

edited Apr 10, 2012 at 5:35

answered Apr 10, 2012 at 5:29

Jay

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1 Comment

Bichvan Nguyen Over a year ago

Thank you, Jay. This solution works! It gets me motivated to learn more about Regular Expression.

Soul Reaver · Accepted Answer · 2012-04-10 05:29:02Z

0

if it's always in this sheme, then faster would be String.Replace:

string sin = "Attributes["412324 - PENNDOT I-95", "Category"].Value, Attributes["412324 - PENNDOT I-95", "Category"].Code";
string sout = sin.Replace("\", \"","\". \"");

you can do the same with RegEx, but it would be slower and still it can break if the input string changes it's structure

answered Apr 10, 2012 at 5:29

Soul Reaver

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3 Comments

Darko Over a year ago

This is a valid solution, but I disagree with your last comment. Your solution would break more readily than a good regex solution.

Soul Reaver Over a year ago

yes, I know about that, RegEx will work in most general cases, but if input string will always look like this - OP can consider using this, much simpler (and faster) solution. Anyway, obwiously correct answer to OP's question is Jay's answer - it makes heavy use of RegEx to replace only correct commas

Bichvan Nguyen Over a year ago

As you mention, this solution should work, however, sometimes, the input string may / may not have extra spaces and the quotion marks could be single quotes. I didn't make it clear in my question.

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