Regex escape with \ or \\?

by

C# does not have a special syntax for construction of regular expressions, like Perl, Ruby or JavaScript do. It instead uses a constructor that takes a string. However, strings have their own escaping mechanism, because you want to be able to put quotes inside the string. Thus, there are two levels of escaping.

So, in a regular expression, w means the letter “w”, while \w means a word character. However, if you make a string "\w", you are escaping the character “w”, which makes no sense, since character “w” is not a quote or a backslash, so "w" == "\w". Then this string containing only “w” gets passed to the regexp constructor, and you end up matching the letter “w” instead of any word character. Thus, to pass the backslash to regexp, you need to put in two backslashes in the string literal (\\w): one will be removed when the string literal is interpreted, one will be used by the regular expression.

When working with regular expressions directly (such as on most online regexp testers, or when using verbatim strings @"..."), you don’t have to worry about the interpretation of string literals, and you always write just one backslash (except when you want to match the backslash itself, but then you’re espacing the backslash for the regexp, not for the string).

More Related Contents:

  1. extract number out strings c# [closed]
  2. RegEx to remove key and certificate headers and footers [duplicate]
  3. c# Regular Expression for the text below? [closed]
  4. Get string between two strings in a string
  5. Using RegEx to balance match parenthesis
  6. Using String Format to show decimal up to 2 places or simple integer
  7. Regular expression to check if password is “8 characters including 1 uppercase letter, 1 special character, alphanumeric characters”
  8. Find a string between 2 known values
  9. Regex to get NUMBER only from String
  10. Regex that accepts only numbers (0-9) and NO characters [duplicate]
  11. C# regex to remove non – printable characters, and control characters, in a text that has a mix of many different languages, unicode letters
  12. Getting overlapping regex matches in C#
  13. Need to perform Wildcard (*,?, etc) search on a string using Regex
  14. Regex that matches a newline (\n) in C#
  15. When not to use Regex in C# (or Java, C++, etc.)
  16. Regex to match all us phone number formats
  17. How to remove numbers from string using Regex.Replace?
  18. Regular Expression to get the SRC of images in C#
  19. Multiline regular expression in C# [duplicate]
  20. .Net regex: what is the word character \w?
  21. Regex: Repeated capturing groups
  22. Canadian postal code validation
  23. Regex to match a word with + (plus) signs
  24. c# regex matches example
  25. Regex Non-Greedy (Lazy)
  26. C# Regex to match the word with dot
  27. C# Regex Issue “unrecognized escape sequence”
  28. Regex for extracting certain part of a String
  29. Regex to match multiple strings
  30. C# Regex, Unrecognized escape sequence

Leave a Comment