CODEWITHSUNDEEP
c#regex
Sudhir Somu
Sudhir Somu

Reputation: 71

Regex.IsMatch returns two different output in C#

I'm trying to find match between a string and pattern using Regex.IsMatch(). I framed the regex and tested it using regex101.com it works fine. Now problem is that Regex.IsMatch(filename, curSetting.RegExMatch.ToString()); returns true curSetting.RegExMatch.IsMatch(filename)) returns false for same filename. Can someone explain how does this differ and what is the difference between them?

RegExMatch is my regex member of curSetting object. Test data in my case is Pattern is 

Gen(?!.*(?:erallog))(?<SerialNo>.+?)-(?<Year>(?:\d{2}))(?<Month>\d{2})(?<Day>\d{‌2})(?<Other>.*?\.log‌)

The string is 1_GeneralLog1370013-170403.log.

Upvotes: 3

Views: 358

Answers (1)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626893

It is clear that your curSetting.RegExMatch is compiled with a RegexOptions.IgnoreCase flag: the (?!.*(?:erallog)) is handled case-insensitively and matches the eralLog in your 1_GeneralLog1370013-170403.log input string, so the negative lookahead pattern finds a match and fails the overall match.

So, there are 2 ways out (depending on what you need):

  • Either remove the RegexOptions.IgnoreCase from the regex object initialization or

  • Add the case-insensitive inline option (?i) into the pattern:

    (?i)Gen(?!.*(?:erallog))(?<SerialNo>.+?)-(?<Year>(?:\d{2}))(?<Mo‌nth>\d{2})(?<Day>\d{2})(?<Other>.*?\.log)

Upvotes: 2

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