C# Essentials

Appendix B. Regular Expressions

The following tables summarize the regular-expression grammar and syntax supported by the regular-expression classes in System.Text. RegularExpression. Each of the modifiers and qualifiers in the tables can substantially change the behavior of the matching and searching patterns. For further information on regular expressions, we recommend the definitive Mastering Regular Expressions by Jeffrey E. F. Friedl (O’Reilly & Associates).

All the syntax described in the tables should match the Perl5 syntax, with specific exceptions noted.

Table B-1. Character Escapes

Escape Code Sequence	Meaning	Hexadecimal Equivalent
\a	Bell	\u0007
\b	Backspace	\u0008
\t	Tab	\u0009
\r	Carriage return	\u000A
\v	Vertical tab	\u000B
\f	Form feed	\u000C
\n	Newline	\u000D
\e	Escape	\u001B
\040	ASCII character as octal
\x20	ASCII character as hex
\cC	ASCII control character
\u0020	Unicode character as hex
\non-escape	A nonescape character

Special case: within a regular expression, \b means word boundary, except in a [] set, where \b means the backspace character.

Table B-2. Substitutions

Expression	Meaning
$group-number	Substitutes last substring matched by group-number
${group-name}	Substitutes last substring matched by (?< group-name >)

Substitutions are specified only within a replacement pattern.

Table B-3. Character Sets

Expression	Meaning
.	Matches any character except \n
[characterlist]	Matches a single character in ...