Regex Match Pattern in c#

Question

Hey I have the following strings as input:

"abcol"  
"ab_col"  
"cold"  
"col_ab"  
"col.ab"

I have the string col to search from. I'm using regex to match

Match matchResults = Regex.Match(input , "col", RegexOptions.IgnoreCase);

I want to match only the string that has this pattern [Any special character or nothing ] + col + [Any special character or nothing]

From the above inputs, I want to return only ab_col, col_ab , col.ab

Any help is highly appreciated.
Thanks

[Any special character] = [^A-Za-z0-9]

Not an alpha numeric character [^A-Za-z0-9] (anything that's not an alphabet or number) — user1178492
– user1178492, Commented Dec 3, 2012 at 19:38
You have not specified what you have tried, and neither are you asking a proper question, but rather saying "solve this for me". I understand that this can be tricky to get right, but this question could probably be solved if you searched around the Internet before asking. — Patrick
– Patrick, Commented Dec 3, 2012 at 19:43
Using [^A-Za-z0-9] I was able to get partially what I want. I'm familiar with Regex and I tried searching the internet. I know I have to use the "|" but not sure exactly how. That's why I posted here. Thanks for your feedback. — user1178492
– user1178492, Commented Dec 3, 2012 at 19:54

Rohit Jain · Accepted Answer · 2012-12-03 19:53:34Z

5

You can use this regex: -

(?:^.*[^a-zA-Z0-9]|^)col(?:[^a-zA-Z0-9].*$|$)

Explanation : -

(?:   // non-capturing
  ^   // match at start of the string
  .*[^a-zA-Z0-9]  // match anything followed by a non-alphanumeric before `col`
    |     // or
  ^       // match the start itself (means nothing before col)
)
  col  // match col
(?:   // non-capturing
  [^a-zA-Z0-9].*  // match a non-alphanumeric after `col` followed by anything
   $     // match end of string
   |     // or
   $     // just match the end itself (nothing after col)
)

edited Dec 3, 2012 at 19:53

answered Dec 3, 2012 at 19:39

Rohit Jain

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Comments

pstrjds · Accepted Answer · 2012-12-03 19:52:18Z

2

@"(^|.*[\W_])col([\W_].*|$)" this is your pattern. \w is alphanumeric character and \W is non alphanumeric character. ^ means line start and $ means line end. | is the or. so (^|.*\W) means line start or some characters and non alphanumeric after them.

EDIT:

yes, underline is alphanumeric too... so you should write [\W_] (non alphanumeric or underline) instead of \W

edited Dec 3, 2012 at 19:52

pstrjds

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answered Dec 3, 2012 at 19:38

shift66

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4 Comments

pstrjds Over a year ago

This will not satisfy the requirement that "ab_col" be a match or "col_ab", because '_' is included in the '\w' class.

pstrjds Over a year ago

Just ran your edit again, still fails. It will match "ab.col", but not "ab_col". Its due to the use of the '\W' class which says "don't match '_'"

user1178492 Over a year ago

\W skips underscores as well which I don't want

pstrjds Over a year ago

@user1178492 - If you group it (which is what I added when I edited the answer) so that instead of \W you have [\W_] it will match the underscore. I like this one over [^a-zA-Z-0-9] just because it is more compact, but some may find the full listing more readable in the long run.

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