C # Regular Expression classic classification collection page 1/3

For a while, regular expression learning was very popular. At that time, I could see several regular expression posts in one day at CSDN, during that time, I learned some basic knowledge through the C # string and regular expression reference manual published by the Forum and Wrox Press, and earned about 1000 points in CSDN, today, when I went to the "C # string and regular expression Reference Manual", I was missing it.
(1) "@" symbol
Symbol below two ows table research room hot, when the morning at "@" although not the C # Regular Expression of the "member", but it often with C # Regular Expression out of double inbound. "@" Indicates that the string following it is a "verbatim string", which is not very understandable. For example, the following two statements are equivalent:
String x = "D :\\ My Huang \ My Doc ";
String y = @ "D: \ My Huang \ My Doc ";
In fact, C # will report an error if it is declared as follows, because "\" is used in C # To implement escape, such as "\ n" line feed:
String x = "D: \ My Huang \ My Doc ";

(2) Basic syntax characters.
\ D 0-9 digits
The complete set of \ D \ d (take all the characters as the complete set, the same below), that is, all non-numeric characters
\ W characters, which are uppercase/lowercase letters, 0-9 digits, and underscores
Set of \ W \ w
\ S blank characters, including line breaks \ n, carriage returns \ r, tabs \ t, vertical tabs \ v, line breaks \ f
Set of \ S \ s
. Any character except linefeed \ n
[…] Match All characters listed in []
[^…] Match characters not listed in []
The following provides some simple examples:
Copy codeThe Code is as follows:
String I = "\ n ";
String m = "3 ";
Regex r = new Regex (@ "\ D ");
// Same as Regex r = new Regex ("\ D ");
// R. IsMatch (I) Result: true
// R. IsMatch (m) Result: false

String I = "% ";
String m = "3 ";
Regex r = new Regex ("[a-z0-9]");
// Match lowercase letters or numbers
// R. IsMatch (I) Result: false
// R. IsMatch (m) Result: true

3) Positioning characters
"Positioning character" represents a virtual character, which represents a location, you can also intuitively think that "positioning character" represents the tiny gap between a character and character.
^ Indicates that the character after it must be at the beginning of the string
$ Indicates that the character before it must be at the end of the string
\ B matches the boundary of a word
\ B matches a non-word boundary
In addition, the character before \ A must be at the beginning of the character, and the character before \ z must be at the end of the string, the character before \ Z must be at the end of the string or before the line break
The following provides some simple examples:
Copy codeThe Code is as follows:
String I = "Live for nothing, die for something ";
Regex r1 = new Regex ("^ Live for nothing, die for something $ ");
// R1.IsMatch (I) true
Regex r2 = new Regex ("^ Live for nothing, die for some $ ");
// R2.IsMatch (I) false
Regex r3 = new Regex ("^ Live for nothing, die for some ");
// R3.IsMatch (I) true

String I = @ "Live for nothing,
Die for something "; // multiple rows
Regex r1 = new Regex ("^ Live for nothing, die for something $ ");
Console. WriteLine ("r1 match count:" + r1.Matches (I). Count); // 0
Regex r2 = new Regex ("^ Live for nothing, die for something $", RegexOptions. Multiline );
Console. WriteLine ("r2 match count:" + r2.Matches (I). Count); // 0
Regex r3 = new Regex ("^ Live for nothing, \ r \ ndie for something $ ");
Console. WriteLine ("r3 match count:" + r3.Matches (I). Count); // 1
Regex r4 = new Regex ("^ Live for nothing, $ ");
Console. WriteLine ("r4 match count:" + r4.Matches (I). Count); // 0
Regex r5 = new Regex ("^ Live for nothing, $", RegexOptions. Multiline );
Console. WriteLine ("r5 match count:" + r5.Matches (I). Count); // 0
Regex r6 = new Regex ("^ Live for nothing, \ r \ n $ ");
Console. WriteLine ("r6 match count:" + r6.Matches (I). Count); // 0
Regex r7 = new Regex ("^ Live for nothing, \ r \ n $", RegexOptions. Multiline );
Console. WriteLine ("r7 match count:" + r7.Matches (I). Count); // 0
Regex r8 = new Regex ("^ Live for nothing, \ r$ ");
Console. WriteLine ("r8 match count:" + r8.Matches (I). Count); // 0
Regex r9 = new Regex ("^ Live for nothing, \ r$", RegexOptions. Multiline );
Console. WriteLine ("r9 match count:" + r9.Matches (I). Count); // 1
Regex r10 = new Regex ("^ die for something $ ");
Console. WriteLine ("r10 match count:" + r10.Matches (I). Count); // 0
Regex r11 = new Regex ("^ die for something $", RegexOptions. Multiline );
Console. WriteLine ("r11 match count:" + r11.Matches (I). Count); // 1
Regex r12 = new Regex ("^ ");
Console. WriteLine ("r12 match count:" + r12.Matches (I). Count); // 1
Regex r13 = new Regex ("$ ");
Console. WriteLine ("r13 match count:" + r13.Matches (I). Count); // 1
Regex r14 = new Regex ("^", RegexOptions. Multiline );
Console. WriteLine ("r14 match count:" + r14.Matches (I). Count); // 2
Regex r15 = new Regex ("$", RegexOptions. Multiline );
Console. WriteLine ("r15 match count:" + r15.Matches (I). Count); // 2
Regex r16 = new Regex ("^ Live for nothing, \ r$ \ n ^ die for something $", RegexOptions. Multiline );
Console. WriteLine ("r16 match count:" + r16.Matches (I). Count); // 1
// For a multi-line string, after the Multiline option is set, ^ and $ match multiple times.

String I = "Live for nothing, die for something ";
String m = "Live for nothing, die for some thing ";
Regex r1 = new Regex (@ "\ bthing \ B ");
Console. WriteLine ("r1 match count:" + r1.Matches (I). Count); // 0
Regex r2 = new Regex (@ "thing \ B ");
Console. WriteLine ("r2 match count:" + r2.Matches (I). Count); // 2
Regex r3 = new Regex (@ "\ bthing \ B ");
Console. WriteLine ("r3 match count:" + r3.Matches (m). Count); // 1
Regex r4 = new Regex (@ "\ bfor something \ B ");
Console. WriteLine ("r4 match count:" + r4.Matches (I). Count); // 1
// \ B is usually used to constrain a complete word