Regex replace help

[Julius Fuchs]

Hi,

I have a string like "bla<cut>blubb< cut>bla<cut>blu bb" and want to replace
the substring from the first occurrence of <cut> to the second with "TEST"
in order to get "blaTESTbla<cut >blubb".
So far I only managed to get blaTESTblubb:

Regex iRegex = new Regex("<cut>.*< cut>");
return iRegex.Replace( "bla<cut>blubb< cut>bla<cut>blu bb", "TEST");

[Martin Honnen]

Julius Fuchs wrote:

Regex iRegex = new Regex("<cut>.*< cut>");

You want non-greedy matching I think
Regex iRegex = new Regex("<cut>.*? <cut>");
--

Martin Honnen --- MVP XML
http://JavaScript.FAQTs.com/

[Julius Fuchs]

Martin Honnen wrote:

You want non-greedy matching I think
Regex iRegex = new Regex("<cut>.*? <cut>");

Thanks for your answer but that's not exactly what I wanted. Imagine the
following string: "a<cut>b<cut>c< cut>d<cut>e", with "<cut>.*?<c ut>" as
pattern I would get "aTESTcTEST e" instead of "aTESTc<cut>d<c ut>e" what I
want.

[AlanT]

The lazy (non-greedy) match indicated by Martin works but the lazy
matches are generally much slower than that standard (greedy) matches.

If performance is an issue you might look at

Regex iRegex = new Regex("<cut>\b\ w*\b<cut>");

The \b (word boundary) prevents matching across multiple <cut> tags
NOTE: This will not find empty pairs (e.g. in bla<cut><cut>dd sd<cut>,
it will not find the <cut><cut>)

or

Regex iRegex = new Regex("<cut>((? !<cut>).)*<cut> ")

where the negative lookahead prevents us passing the middle <cut>.
NOTE: This will find the empty pair

hth,
Alan

[AlanT]

Use

return iRegex.Replace( "a<cut>b<cut>c< cut>d<cut>e", "TEST", 1);

This will return the string with only the first match replaced.

aTESTc<cut>d<cu t>e

hth,
Alan.