What is the role of regular expressions in C#? What do the matching characters mean?

The content of this article is to introduce what are the functions of regular expressions in C#? What do the matching characters mean? It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

1. The role of regular expressions: Used to describe the characteristics of strings.

2, The meaning of each matching character:

. : Represents a single character except \n

[ ] : Indicates that any single character listed in the character array [] can be selected

| : Indicates the meaning of "or"

() : Indicates changing the priority or "extracting group"

* : Limiting the previous expression to appear 0 or more times

: Limit the previous expression to appear one or more times

? : Limit the previous expression to appear 0 or 1 times

^: Indicates that it starts with an expression (for example: ^http means that the string starts with "http")

$ : Indicates that it ends with an expression (for example: com$ means that the string ends with "com")

\d : Lowercase \d means 0 Numbers between -9

\D: uppercase \D represents characters other than 0-9

\w: lowercase \w Represents [a-zA-Z0-9]

\W: Uppercase \W represents characters other than [a-zA-Z0-9]

\s: Lowercase \s represents invisible characters (such as spaces, tabs, \r\n...)

\S: Uppercase \S represents characters other than invisible characters

3, Regular expression example

Matching postal code: ^[0-9]{6}$

Match numbers between 10 and 25: ^(1[0-9]|2[0-5])$

Approximately match the email format: ^[a-zA-Z0- 9_] @[a-zA-Z0-9] (\.[a-zA-Z0-9] ){1,2}$

4, Use regular expressions to match strings

Need to quote: System.Text.RegularExpressions;

Regex.IsMatch()Method: to determine whether the given string matches a regular expression

Regex.Match()Method: Extract a string matching the regular expression from the given string

Regex.Matches( )Method: Extract all strings matching the regular expression from the given string

Regex.Replace()Method: Replace all strings matching the regular expression The string is another string

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