/CS_DotNetRegularExpressionsProjectsAndSolutions

book example

Primary LanguageC#

CS_DotNetRegularExpressionsProjectsAndSolutions

book example

.Net RegularExpression Quick Reference

https://docs.microsoft.com/ko-kr/dotnet/standard/base-types/regular-expression-language-quick-reference

Example codes

https://docs.microsoft.com/ko-kr/dotnet/standard/base-types/character-classes-in-regular-expressions

unicode 8.0

https://www.unicode.org/versions/Unicode8.0.0/

Case sensitive

  • Regular expression is basically case sensitive. I should turn it on when I need case insensitive comparison Option1: Specify as part of pattern inline directive(?i)A Option2: Regex.IsMatch(text, pattern, RegexOptions.IgnoreCase

Single Characters

  1. Single Character "OR" condition
  • Problem: Find all occurrences of letter 'a' or 'b'
  • Pattern: a|b
  • Text: this is a big text
  1. String literal
  • Problem: Find all occurrences of string 'ab'
  • Pattern: ab
  • Text: this is absolute test
  1. Set based - Square brackeets [set membership]
  • Problem: Find all occurrences of a or b
  • Pattern: [ab]
  • Text: this is a big test
  1. Set based - Negation '^'

  • Problem: Find all occurrences of characters that are NOT (a or b)

  • Pattern [^ab]

  • Text: this is a big test

  • needs to be first character inside the set

  • Pattern: [a^b] => indicates a set with members(a, b, ^) and will match a literal ^
  • Text: this is a ^ big test
  1. Range of characters
  • Problem: Find all occurrences of (a, b, c, d)
  • Pattern: [a-d] (is equal to [abcd])
  • Text: this is a definitive test
  1. Multiple range of characters

  • Problem: find all occurrences of (a, b, c, d, x, y, z, 0, 1, 2, 3)

  • Pattern: [a-dx-z0-3]

  • Text: x-ray 3 won't work for this test

  • Negate the whole range with ^

  • Problem: Find all occurrences of characters not in (a, b, c, d, x, y, z, 0, 1, 2, 3)

  • Pattern: [^a-dx-z0-3]

  1. Whild card character . <= Dot!
  • Dot or full stop character matches every character except new line \n
  • Dot may have a performance issue. Use carefullly.
  1. Escape with \
  • Problem: Find all occurrences of '.'(dot)
  • Pattern: .
  • Text: This. Is a Test.
  1. Control Characters(tab, newline, carriage return and so forth)
  • Problem: Find all occurrences of tab
  • Pattern: \t
  • Text: One .Two

Anchors

  1. Anchors are special syntex used for specifying.
  • Start of string or line
  • End of string or line
  • Word boundary
  • And so forth...
  1. Search for text
  • Problem: Find all occurrences of word 'log'
  • Pattern: log
  • Text: catalog of log
  1. Word boundary
  • Pattern: \blog\b => is instruction to match only on word boundary
  • Text: catalog of log
  1. Start of string or line ^
  • Problem: Find occurrences of 'apple' at beginning of string or line
  • Pattern: ^apple
  • Text: apple Grows on apple tree
  1. ^ - Multi-line Text
  • Pattern: ^apple
  • Text: apple 1 grows on apple tree apple 2 grows on apple tree
  • Internal String: "apple 1 grows on apple tree\r\napple 2 grows on apple tree\r\n" + Windows uses \r\n to represent new line => need to turn-on multi-line mode to interprete embedded lines
  1. ^ - Turn on multi-line mode (?m)
  • Problem: Find occurrences of 'apple' at beginning of string or line
  • Pattern: (?m)^apple
  • Text: apple 1 grows on apple tree apple 2 grows on apple tree
  1. End of string or line $(matches end of string or \n)
  • Problem: Find occurrences of 'apple' at end of string or line
  • Patten: apple$
  • Text: apple apple
  1. End of string or line $ (matches end of string or \n)
  • Problem: Find occurrences of 'apple' at end of string or line
  • Pattern: apple$
  • Text: apple apple
  1. $ - Multi-line text
  • Problem: Find occurrences of 'apple' at end of string or line
  • Pattern: apple$
  • Text: apple apple
  • Internal String: "apple\r\napple"
  1. $ - Turn on multi-line mode (?m) and include \r as optional character
  • Problem: Find occurrences of 'apple' at end of string or line
  • Pattern: (?m)apple\r?$ ($ 사인은 \n 또는 end of string만 캐치한다. 하지만 윈도우즈는 \r\n을 줄바꿈으로 쓰므로 \r?이 필요)
  • Text: apple appple

Character Classes

  • Characer classes are readymade shortcuts that represents a set of characters
  1. Decimal Digit \d
  • Problem: Check if valid decimal digit(0-9)
  • Pattern 1: [0123456789]
  • Pattern 2: [0-9]
  • Pattern 3: \d
  • Not a decimal digit: \D
  1. Word Character \w
  • Problem: Check i a character is a valid letter of an alphabet (any language) or digit(숫자도 포함한다)
  • Pattern: \w
  • Text: F16, F18, ㄱ, ㄴ
  • Not a character: \W
  1. Whtie space character \s
  • Matches space, tab, carriage return, new line and so forth
  • Problem: Check for white space character
  • Pattern: \s
  • Text: One tab space Two tab
  • Not a white space character: \S
  1. Unicode category or Block \p{category}

  • Problem: Find occurrences of punctuation characters(구분문자)

  • Pattern: \p{P} => 구분문자 전체

  • Text: "one,two;three!FOUR?Five*" => ",;!?*"

  • Problem: Find uppercase characters

  • Pattern: \p{Lu} => 대문자 영어

  • Text: "one,two;three!FOUR?Five*"