\a

Matches a bell character, \u0007.

\a

"\u0007" in "Error!" + '\u0007'

\b

In a character class, matches a backspace, \u0008.

[\b]{3,}

"\b\b\b\b" in "\b\b\b\b"

\t

Matches a tab, \u0009.

(\w+)\t

"item1\t", "item2\t" in "item1\titem2\t"

\r

Matches a carriage return, \u000D. (\r is not equivalent to the newline character, \n.)

\r\n(\w+)

"\r\nThese" in "\r\nThese are\ntwo lines."

\v

Matches a vertical tab, \u000B.

[\v]{2,}

"\v\v\v" in "\v\v\v"

\f

Matches a form feed, \u000C.

[\f]{2,}

"\f\f\f" in "\f\f\f"

\n

Matches a new line, \u000A.

\r\n(\w+)

"\r\nThese" in "\r\nThese are\ntwo lines."

\e

Matches an escape, \u001B.

\e

"\x001B" in "\x001B"

\ nnn

Uses octal representation to specify a character (nnn consists of up to three digits).

\w\040\w

"a b", "c d" in

"a bc d"

\xnn

Uses hexadecimal representation to specify a character (nn consists of exactly two digits).

\w\x20\w

"a b", "c d" in

"a bc d"

\cX

\c x

Matches the ASCII control character that is specified by X or x, where X or x is the letter of the control character.

\cC

"\x0003" in "\x0003" (Ctrl-C)

\unnnn

Matches a Unicode character by using hexadecimal representation (exactly four digits, as represented by nnnn).

\w\u0020\w

"a b", "c d" in

"a bc d"

\

When followed by a character that is not recognized as an escaped character in this and other tables in this topic, matches that character. For example, \* is the same as \x2A. This allows the regular expression engine to disambiguate language elements (such as * or ?) and character literals (represented by \* or \?).

\d+[\+-x\*]\d+\d+[\+-x\*\d+

"2+2" and "3*9" in "(2+2) * 3*9"

[ character_group ]

Matches any single character in character_group. By default, the match is case-sensitive.

[ae]

"a" in "gray"

"a", "e" in "lane"

[^ character_group]

Negation: Matches any single character that is not in character_group. By default, characters in character_group are case-sensitive.

[^aei]

"r", "g", "n" in "reign"

[ first - last ]

Character range: Matches any single character in the range from first to last.

[A-Z]

"A", "B" in "AB123"

.

Wildcard: Matches any single character except \n.

a.e

"ave" in "nave"

"ate" in "water"

\p{ name}

Matches any single character in the Unicode general category or named block specified by name.

\p{Lu}

\p{IsCyrillic}

"C", "L" in "City Lights"

"Д", "Ж" in "ДЖem"

\P{ name}

Matches any single character that is not in the Unicode general category or named block specified by name.

\P{Lu}

\P{IsCyrillic}

"i", "t", "y" in "City"

"e", "m" in "ДЖem"

\w

Matches any word character.

\w

"I", "D", "A", "1", "3" in "ID A1.3"

\W

Matches any non-word character.

\W

" ", "." in "ID A1.3"

\s

Matches any white-space character.

\w\s

"D " in "ID A1.3"

\S

Matches any non-white-space character.

\s\S

" _" in "int __ctr"

\d

Matches any decimal digit.

\d

"4" in "4 = IV"

\D

Matches any character that is not a decimal digit.

\D

" ", "=", " ", "I", "V" in "4 = IV"

^

The match must start at the beginning of the string or line.

^\d{3}

"901-" in

"901-333-"

$

The match must occur at the end of the string or before \n at the end of the line or string.

-\d{3}$

"-333" in

"-901-333"

\A

The match must occur at the start of the string.

\A\d{3}

"901" in

"901-333-"

\Z

The match must occur at the end of the string or before \n at the end of the string.

-\d{3}\Z

"-333" in

"-901-333"

\z

The match must occur at the end of the string.

-\d{3}\z

"-333" in

"-901-333"

\G

The match must occur at the point where the previous match ended.

\G\(\d\)

"(1)", "(3)", "(5)" in "(1)(3)(5)[7](9)"

\b

The match must occur on a boundary between a \w (alphanumeric) and a \W (nonalphanumeric) character.

\b\w+\s\w+\b

"them them" in "them theme them them"

\B

The match must not occur on a \b boundary.

\Bend\w*\b

"ends", "ender" in "end sends endure lender"

( subexpression )

Captures the matched subexpression and assigns it a zero-based ordinal number.

(\w)\1

"ee" in "deep"

(?< name >subexpression)

Captures the matched subexpression into a named group.

(?<double>\w)\k<double>

"ee" in "deep"

(?< name1 -name2 > subexpression)

Defines a balancing group definition. For more information, see the "Balancing Group Definition" section in Grouping Constructs.

(((?'Open'\()[^\(\)]*)+((?'Close-Open'\))[^\(\)]*)+)*(?(Open)(?!))$

"((1-3)*(3-1))" in "3+2^((1-3)*(3-1))"

(?: subexpression)

Defines a noncapturing group.

Write(?:Line)?

"WriteLine" in "Console.WriteLine()"

(?imnsx-imnsx: subexpression)

Applies or disables the specified options within subexpression. For more information, see Regular Expression Options.

A\d{2}(?i:\w+)\b

"A12xl", "A12XL" in "A12xl A12XL a12xl"

(?= subexpression)

Zero-width positive lookahead assertion.

\w+(?=\.)

"is", "ran", and "out" in "He is. The dog ran. The sun is out."

(?! subexpression)

Zero-width negative lookahead assertion.

\b(?!un)\w+\b

"sure", "used" in "unsure sure unity used"

(?<= subexpression)

Zero-width positive lookbehind assertion.

(?<=19)\d{2}\b

"99", "50", "05" in "1851 1999 1950 1905 2003"

(?<! subexpression)

Zero-width negative lookbehind assertion.

(?<!19)\d{2}\b

"51", "03" in "1851 1999 1950 1905 2003"

(?> subexpression)

Nonbacktracking (or "greedy") subexpression.

[13579](?>A+B+)

"1ABB", "3ABB", and "5AB" in "1ABB 3ABBC 5AB 5AC"

*

Matches the previous element zero or more times.

\d*\.\d

".0", "19.9", "219.9"

+

Matches the previous element one or more times.

"be+"

"bee" in "been", "be" in "bent"

?

Matches the previous element zero or one time.

"rai?n"

"ran", "rain"

{ n }

Matches the previous element exactly n times.

",\d{3}"

",043" in "1,043.6", ",876", ",543", and ",210" in "9,876,543,210"

{ n ,}

Matches the previous element at least n times.

"\d{2,}"

"166", "29", "1930"

{ n ,m }

Matches the previous element at least n times, but no more than m times.

"\d{3,5}"

"166", "17668"

"19302" in "193024"

*?

Matches the previous element zero or more times, but as few times as possible.

\d*?\.\d

".0", "19.9", "219.9"

+?

Matches the previous element one or more times, but as few times as possible.

"be+?"

"be" in "been", "be" in "bent"

??

Matches the previous element zero or one time, but as few times as possible.

"rai??n"

"ran", "rain"

{ n }?

Matches the preceding element exactly n times.

",\d{3}?"

",043" in "1,043.6", ",876", ",543", and ",210" in "9,876,543,210"

{ n ,}?

Matches the previous element at least n times, but as few times as possible.

"\d{2,}?"

"166", "29", "1930"

{ n ,m }?

Matches the previous element between n and m times, but as few times as possible.

"\d{3,5}?"

"166", "17668"

"193", "024" in "193024"

\ number

Backreference. Matches the value of a numbered subexpression.

(\w)\1

"ee" in "seek"

\k< name >

Named backreference. Matches the value of a named expression.

(?<char>\w)\k<char>

"ee" in "seek"

|

Matches any one element separated by the vertical bar (|) character.

th(e|is|at)

"the", "this" in "this is the day. "

(?( expression ) yes | no )

Matches yes if expression matches; otherwise, matches the optional no part. expression is interpreted as a zero-width assertion.

(?(A)A\d{2}\b|\b\d{3}\b)

"A10", "910" in "A10 C103 910"

(?( name) yes | no)

Matches yes if the named capture name has a match; otherwise, matches the optional no.

(?<quoted>")?(?(quoted).+?"|\S+\s)

Dogs.jpg, "Yiska playing.jpg" in "Dogs.jpg "Yiska playing.jpg""

$ number

Substitutes the substring matched by group number.

\b(\w+)(\s)(\w+)\b

$3$2$1

"one two"

"two one"

${ name }

Substitutes the substring matched by the named group name.

\b(?<word1>\w+)(\s)(?<word2>\w+)\b

${word2} ${word1}

"one two"

"two one"

$$

Substitutes a literal "$".

\b(\d+)\s?USD

$$$1

"103 USD"

"$103"

$&

Substitutes a copy of the whole match.

(\$*(\d*(\.+\d+)?){1})

**$&

"$1.30"

"**$1.30**"

$`

Substitutes all the text of the input string before the match.

B+

$`

"AABBCC"

"AAAACC"

$'

Substitutes all the text of the input string after the match.

B+

$'

"AABBCC"

"AACCCC"

$+

Substitutes the last group that was captured.

B+(C+)

$+

"AABBCCDD"

AACCDD

$_

Substitutes the entire input string.

B+

$_

"AABBCC"

"AAAABBCCCC"

(?imnsx-imnsx)

Sets or disables options such as case insensitivity in the middle of a pattern. For more information, see Regular Expression Options.

\bA(?i)b\w+\b matches "ABA", "Able" in "ABA Able Act"

(?# comment)

Inline comment. The comment ends at the first closing parenthesis.

\bA(?#Matches words starting with A)\w+\b

# [to end of line]

X-mode comment. The comment starts at an unescaped # and continues to the end of the line.

(?x)\bA\w+\b#Matches words starting with A