Using a regular expression to retrieve the text between two parentheses

[Mark Rae]

Hi,

Supposing I had a string made up of a person's name followed by their
profession in parentheses e.g.

string strText = "Tiger Woods (golfer)";

and I wanted to extract the portion of the string between the parentheses
i.e. "golfer"

Would a regular expression be the most efficient way of doing this...?

I'm trying to do something like this:

string strProfession = String.Empty;
Regex objRegEx = new Regex("(((.|\n) *?))", RegexOptions.Ig noreCase);
foreach (Match objMatch in objRegEx.Matche s(strText)
{
strProfession = objMatch.ToStri ng();
}

but that is returning an empty string, no doubt because I haven't defined
the regular expression correctly.

Also, is it even necessary to have a foreach loop here, as in this
particular scenario there can only ever be one match...?

Any assistance gratefully received.

Mark

[Jon Shemitz]

Mark Rae wrote:

@"\( ([^\)]+) \)", RegexOptions.Ig norePatternWhit espace

is probably a bit simpler and faster - there's no real need to capture
the parens.

That returns an empty string...

No, it doesn't. The Match.Value is the parenthesized expression;
Match.Groups[1].Value is the string in the parens.

--

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www.midnightbeach.com/.net

[Jon Shemitz]

Gary Stephenson wrote:

But perhaps you should be made aware of the limitations implicit in
regexes - the main one being commonly rendered as "regexes can't count". As
long as you are not having to deal with recursive structures, nested
delimiters and so on, regexes will often work well. But they can't be used
to "find the balancing brace", verify correct nesting or suchlike.

Not true with .NET regexes, btw.

--

..NET 2.0 for Delphi Programmers
www.midnightbeach.com/.net

[Ethan Strauss]

I haven't been following this whole thread, so I may be somewhat off topic,
but it seems relevant...

Don't forget that you can name groups in a Regex.
For example you could take the expression below and add a name as follows
@"\( (?<StuffIWantTo ActuallySee>[^\)]+) \)",
RegexOptions.Ig norePatternWhit espace

You can then get at it from the Group name.
Match.Groups["StuffIWantToAc tuallySee"].Value

I find that much easier to deal with than trying to get the groups by
number.

Ethan

"Jon Shemitz" <jo*@midnightbe ach.comwrote in message
news:45******** ******@midnight beach.com...

Mark Rae wrote:

@"\( ([^\)]+) \)", RegexOptions.Ig norePatternWhit espace

is probably a bit simpler and faster - there's no real need to capture
the parens.

That returns an empty string...

No, it doesn't. The Match.Value is the parenthesized expression;
Match.Groups[1].Value is the string in the parens.

--

.NET 2.0 for Delphi Programmers
www.midnightbeach.com/.net

[Mark Rae]

"Jon Shemitz" <jo*@midnightbe ach.comwrote in message
news:45******** ******@midnight beach.com...

No, it doesn't. The Match.Value is the parenthesized expression;
Match.Groups[1].Value is the string in the parens.

Apologies - my mistake.

[Gary Stephenson]

Not true with .NET regexes, btw.

Really? How so? They must then be fundamentally different to all regex
implementations I have seen or heard about. A quick scan of the
documentation doesn't reveal anything significantly different about .NET
regexes ... hmmm ...

As I understand it, in order to solve matching-brace type problems, a
push-down automaton is required, as opposed to a finite-state automaton. Do
..NET regexes somehow provide that?

Please explain,

respectfully,

gary

[Jon Shemitz]

Gary Stephenson wrote:

Not true with .NET regexes, btw.

As I understand it, in order to solve matching-brace type problems, a
push-down automaton is required, as opposed to a finite-state automaton. Do
.NET regexes somehow provide that?

Yes.

..NET capture groups capture all matching expressions, not just the
last one. The "balancing group definition" grouping construct
(?<-name>expr) pops the most recent capture if expr matches; the
(?(name)a|b) alternation construct lets you force the match to fail if
a stack is not empty.

See pgs 289-290 in
<http://www.midnightbea ch.com/.net/ShemitzBook.Cha pter11.pdffor more
details.

--

..NET 2.0 for Delphi Programmers
www.midnightbeach.com/.net

[Gary Stephenson]

Hi Jon

----- Original Message -----
From: "Jon Shemitz" <jo*@midnightbe ach.com>
Newsgroups: microsoft.publi c.dotnet.langua ges.csharp
Sent: Tuesday, January 16, 2007 12:09 PM
Subject: Re: Using a regular expression to retrieve the text between two
parentheses

.NET capture groups capture all matching expressions, not just the
last one. The "balancing group definition" grouping construct
(?<-name>expr) pops the most recent capture if expr matches; the
(?(name)a|b) alternation construct lets you force the match to fail if
a stack is not empty.

See pgs 289-290 in
<http://www.midnightbea ch.com/.net/ShemitzBook.Cha pter11.pdffor more
details.

Cool as! Thanks for that - very interesting indeed. Apologies to all for
misrepresenting (and underestimating ) .NET regexes.

gary

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