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ột regular expression là một pattern mà regular expression engine cố gắng để match trong văn bản đầu vào. Một pattern bao gồm một hoặc nhiều character literals, operators, or constructs.
Bạn có thẻ tham khảo các bảng character literals, operators, or constructs dưới đây. Sử dụng chúng để tạo một pattern hay cho việc xử lý văn bản:

1. Single characters ↓
2. Control characters ↓
3. Character classes ↓
4. Quantifiers ↓
5. Anchors ↓
6. Groups ↓
7. Inline options ↓
8. Backreferences ↓
9. Alternation ↓
10. Substitution ↓
11. Comments ↓
12. Supported unicode categories ↓
13. Regular expression operations ↓

• a. Pattern matching with Regex objects ↓
• b. Pattern matching with static methods ↓
• c. Finding and replacing matched patterns ↓

1. Single Characters ↑

Use	To match any character
[set]	In that set
[^set]	Not in that set
[a–z]	In the a-z range
[^a–z]	Not in the a-z range
.	Any except \n (new line)
\char	Escaped special character

2. Control Characters ↑

Use	To match	Unicode
\t	Horizontal tab	\u0009
\v	Vertical tab	\u000B
\b	Backspace	\u0008
\e	Escape	\u001B
\r	Carriage return	\u000D
\f	Form feed	\u000C
\n	New line	\u000A
\a	Bell (alarm)	\u0007
\c char	ASCII control character	-

3. Character Classes ↑

Use	To match character
\p{ctgry}	In that Unicode category or block
\P{ctgry}	Not in that Unicode category or block
\w	Word character
\W	Non-word character
\d	Decimal digit
\D	Not a decimal digit
\s	White-space character
\S	Non-white-space char

4. Quantifiers ↑

Greedy	Lazy	Matches
*	*?	0 or more times
+	+?	1 or more times
?	??	0 or 1 time
{n}	{n}?	Exactly n times
{n,}	{n,}?	At least n times
{n,m}	{n,m}?	From n to m times

5. Anchors ↑

Use	To specify position
^	At start of string or line
\A	At start of string
\z	At end of string
\Z	At end (or before \n at end) of string
$	At end (or before \n at end) of string or line
\G	Where previous match ended
\b	On word boundary
\B	Not on word boundary

6. Groups ↑

Use	To define
(exp)	Indexed group
(?<name>exp)	Named group
(?<name1-name2>exp)	Balancing group
(?:exp)	Noncapturing group
(?=exp)	Zero-width positive lookahead
(?!exp)	Zero-width negative lookahead
(?<=exp)	Zero-width positive lookbehind
(?<!exp)	Zero-width negative lookbehind
(?>exp)	Non-backtracking (greedy)

7. Inline Options ↑

Option	Effect on match
i	Case-insensitive
m	Multiline mode
n	Explicit (named)
s	Single-line mode
x	Ignore white space
Use	To
(?imnsx-imnsx)	Set or disable the specified options
(?imnsx-imnsx:exp)	Set or disable the specified options within the expression

8. Backreferences ↑

Use	To match
\n	Indexed group
\k<name>	Named group

9. Alternation ↑

Use	To match
a |b	Either a or b
(?(exp)	yes if exp is matched
yes | no)	no if exp isn't matched
(?(name)	yes if name is matched
yes | no)	no if name isn't matched

10. Substitution ↑

Use	To substitute
$n	Substring matched by group number n
${name}	Substring matched by group name
$$	Literal $ character
$&	Copy of whole match
$`	Text before the match
$'	Text after the match
$+	Last captured group
$_	Entire input string

11. Comments ↑

Use	To
(?# comment)	Add inline comment
#	Add x-mode comment

12. Supported Unicode Categories ↑

Category	Description
Lu	Letter, uppercase
LI	Letter, lowercase
Lt	Letter, title case
Lm	Letter, modifier
Lo	Letter, other
L	Letter, all
Mn	Mark, nonspacing combining
Mc	Mark, spacing combining
Me	Mark, enclosing combining
M	Mark, all diacritic
Nd	Number, decimal digit
Nl	Number, letterlike
No	Number, other
N	Number, all
Pc	Punctuation, connector
Pd	Punctuation, dash
Ps	Punctuation, opening mark
Pe	Punctuation, closing mark
Pi	Punctuation, initial quote mark
Pf	Puntuation, final quote mark
Po	Punctuation, other
P	Punctuation, all
Sm	Symbol, math
Sc	Symbol, currency
Sk	Symbol, modifier
So	Symbol, other
S	Symbol, all
Zs	Separator, space
Zl	Separator, line
Zp	Separator, paragraph
Z	Separator, all
Cc	Control code
Cf	Format control character
Cs	Surrogate code point
Co	Private-use character
Cn	Unassigned
C	Control characters, all

13. Regular Expression Operations ↑

a. Pattern matching with Regex objects ↑

To initialize with	Use constructor
Regular exp	Regex(String)
+ options	Regex(String, RegexOptions)
+ time-out	Regex(String, RegexOptions,

b. Pattern matching with static methods ↑

To	Use method
Validate match	Regex.IsMatch
Retrieve single match	Regex.Match (first)
	Match.NextMatch (next)
Retrieve all matches	Regex.Matches
Replace match	Regex.Replace
Divide text	Regex.Split
Handle char escapes	Regex.Escape
	Regex.Unescape

c. Finding and replacing matched patterns ↑

To get	Use Regex API
Group names	GetGroupNames
	GetGroupNameFromNumber
Group numbers	GetGroupNumbers
	GetGroupNumberFromName
Expression	ToString
Options	Options
Time-out	MatchTimeOut
Cache size	CacheSize
Direction	RightToLeft

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Reference: MSDN
Created: 21/11/2015

[C# Guide] Regular Expression Language

Related Tags :
.NET Regular Expressions