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Explain C# Substitution in regular expression
A regular expression is a pattern that could be matched against an input text. There are various categories of characters, operators, and constructs that let’s you to define regular expressions. Substitutions are used in replacement patterns.
The following table lists the substitutions.
| Character | Description | Pattern | Replacement pattern | Input string | Resulting string |
|---|---|---|---|---|---|
| $number | Substitutes the substring matched by group number. | \b(\w+)(\s)(\w+)\b | $3$2$1 | "one two" | "two one" |
| ${name} | Substitutes the substring matched by the named groupname. | \b(?< word1>\w+)(\s)(?< word2>\w+)\b | ${word2} ${word1} | "one two" | "two one" |
| $$ | Substitutes a literal "$". | \b(\d+)\s?USD | $$$1 | "103 USD" | "$103" |
| $& | Substitutes a copy of the whole match. | (\$*(\d*(\.+\d+)?){1}) | **$& | "$1.30" | "**$1.30**" |
| $` | Substitutes all the text of the input string before the match. | B+ | $` | "AABBCC" | "AAAACC" |
| $' | Substitutes all the text of the input string after the match. | B+ | $' | "AABBCC" | "AACCCC" |
| $+ | Substitutes the last group that was captured. | B+(C+) | $+ | "AABBCCDD" | AACCDD |
| $_ | Substitutes the entire input string. | B+ | $_ | "AABBCC" | "AAAABBCCC |
Updated on: 30-Jul-2019
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