Excluding Items in Search

Question

Hi,

I'm in a dilemma here, I'm trying to search for a string using RegEx but I don't want to include or match items found within a quoted string, here's a sample:

search: dog
input string:
a dog is in the city 'yet there are many dog also' and ther goes the dog

result:
2 matches
the first one is the first occurence of "dog"
the second is the third occurence of "dog"


Based on the sample I don't want to include strings contained in quotes. How can I do that in RegEx? Is it even possible?


Thanks in advance guys...



chow,

Answer 1

Try this...

    string pattern = @"(?>=[^'])*dog(?=([^']*'[^']+')|$)";

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Les Potter, Xalnix Corporation, Yet Another C# Blog

Answer 2

Sorry, I wrote the pattern quickly.  Now that I come back to it I see a flaw.  Here is an updated pattern and a test jig to experiment with it...

string pattern = @"(?>=[^'])*dog(?=[^']*('[^']+'|$))";

string[] tests = {

"this is a dog but 'this is not a dog for our' purposes of a dog",

"this is a dog but",

"'this is not a dog for our' purposes of a dog",

};

foreach (string test in tests)

{

Console.WriteLine(test);

Regex rx = new Regex(pattern, RegexOptions.IgnorePatternWhitespace);

Match mx = rx.Match(test);

while (mx.Success)

{

Console.WriteLine("\t\t{0} {1} {2}", mx.Value, mx.Index, mx.Length);

mx = mx.NextMatch();

}

}

This isn't perfect because your quoted portion of the string could contain "possessive" nouns or contractions or proper names with apostrophes in them.

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Les Potter, Xalnix Corporation, Yet Another C# Blog