C# RegEx Cheat Sheet

Basic Patterns

Pattern	Description
.	Matches any single character except a newline.
^	Matches the start of a string.
$	Matches the end of a string.
*	Matches 0 or more repetitions of the preceding character or group.
+	Matches 1 or more repetitions of the preceding character or group.
?	Matches 0 or 1 repetition of the preceding character or group.
{n}	Matches exactly n repetitions of the preceding character or group.
{n,}	Matches n or more repetitions of the preceding character or group.
{n,m}	Matches between n and m repetitions of the preceding character or group.

Character Classes

Pattern	Description
\d	Matches any digit (0-9).
\D	Matches any non-digit.
\w	Matches any word character (alphanumeric + underscore).
\W	Matches any non-word character.
\s	Matches any whitespace character (spaces, tabs, line breaks).
\S	Matches any non-whitespace character.

Assertions

Pattern	Description
\b	Matches a word boundary.
\B	Matches a non-word boundary.
(?=...)	Positive lookahead.
(?!...)	Negative lookahead.
(?<=...)	Positive lookbehind.
(?	Negative lookbehind.

Groups and Backreferences

Pattern	Description
( ... )	Captures the matched content.
(?: ... )	Non-capturing group.
\1	Backreference to the first capturing group.
\2	Backreference to the second capturing group, and so on.

Character Escapes

Pattern	Description
\a	Matches a bell character (alarm, \x07).
\e	Matches an escape character (\x1B).

Unicode Categories

Pattern	Description
\p{name}	Matches any character in the named category, e.g., \p{Lu} matches any uppercase letter.
\P{name}	Matches any character not in the named category.

Miscellaneous

Pattern	Description
(?...)	Named capturing group.
\k	Backreference to a named group.
(?(expression)yes|no)	Conditional matching.
(?#...)	Inline comment.
(?imnsx-imnsx)	Sets or clears specific options within a subexpression: i (case-insensitive), m (multi-line mode), n (explicit capture), s (single-line mode), x (ignore pattern whitespace).
(?imnsx-imnsx:...)	Group with specific options.

Atomic Grouping and Possessive Quantifiers

Pattern	Description
(?>...)	Atomic group.
*+	Possessive quantifier (0 or more).
++	Possessive quantifier (1 or more).
?+	Possessive quantifier (0 or 1).

Balancing Group Definitions

Pattern	Description
(?...)	Defines a balancing group definition.

Zero-width Positive Lookbehind and Zero-width Negative Lookbehind

Pattern	Description
(?<=...)	Zero-width positive lookbehind.
(?	Zero-width negative lookbehind.

Options

Pattern	Description
(?imnsx-imnsx)	Sets or clears specific options within a subexpression: i (case-insensitive), m (multi-line mode), n (explicit capture), s (single-line mode), x (ignore pattern whitespace).
(?imnsx-imnsx:...)	Group with specific options.

Right-to-left Mode

Pattern	Description
(?<)	Zero-width positive lookbehind assertion.
(?<!)	Zero-width negative lookbehind assertion.

Named Blocks

Pattern	Description
(?<name>...)	Named capturing group.
\k<name>	Backreference to a named group.

Non-capturing Group

Pattern	Description
(?:...)	Non-capturing group.

Atomic Zero-width Assertions

Pattern	Description
(?=...)	Zero-width positive lookahead assertion.
(?!...)	Zero-width negative lookahead assertion.

Comments

Pattern	Description
(?#...)	Inline comment.

Options Setting

Pattern	Description
(?imnsx)	Set the options for the remainder of the regex.
(?-imnsx)	Unset the options for the remainder of the regex.

Conditional Matching

Pattern	Description
(?(expression)yes|no)	Conditional matching.