{"id":1958,"date":"2023-06-02T13:34:51","date_gmt":"2023-06-02T06:34:51","guid":{"rendered":"https:\/\/csharptutorial.net\/?page_id=1958"},"modified":"2023-06-02T13:34:53","modified_gmt":"2023-06-02T06:34:53","slug":"csharp-regex-alternation","status":"publish","type":"page","link":"https:\/\/www.csharptutorial.net\/csharp-regular-expression\/csharp-regex-alternation\/","title":{"rendered":"Regex Alternation"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you will learn how to use regex alternation to match one pattern or another.<\/p>\n\n\n\n

Introduction to the regex alternation<\/h2>\n\n\n\n

Regex alternation is like the OR operator in regular expressions, which allows you to match one pattern or another. Regex alternation is denoted by an alteration operator (|<\/code>):<\/p>\n\n\n

pattern1 | pattern2 | pattern3<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
It is also known as regex OR or regex choice.<\/p>\n\n\n\n
When matching a pattern with an alteration, the regex engine will attempt to match each pattern sequentially from left to right. If a regex pattern finds a match, it stops matching immediately and returns the result.<\/p>\n\n\n\n
Regex alternations are useful when you want to specify multiple options for a pattern to match. <\/p>\n\n\n\n
Regex alternation examples<\/h2>\n\n\n\n
Let’s explore some examples of using the regex alternation.<\/p>\n\n\n\n
1) Using regex alternation to match a specific word<\/h3>\n\n\n\n
The following example uses the regex alteration to match either apple<\/code>, banana<\/code>, or orange<\/code> word in a text:<\/p>\n\n\n
using<\/span> System.Text.RegularExpressions;\nusing<\/span> static<\/span> System.Console;\n\n\nvar<\/span> text = \"apple, banana, orange\"<\/span>;\nvar<\/span> pattern = @\"apple|banana|orange\"<\/span>;\nvar<\/span> matches = Regex.Matches(text, pattern);\n\nforeach<\/span> (var<\/span> match in<\/span> matches)\n{\n    WriteLine(match);\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
It returns three matches:<\/p>\n\n\n
apple\nbanana\norange<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
2) Using regex alternation to match a time string in the format hh:mm<\/h3>\n\n\n\n
The following example uses a regex alternation to match the time string in the format hh:mm<\/code> in a string:<\/p>\n\n\n
using<\/span> System.Text.RegularExpressions;\nusing<\/span> static<\/span> System.Console;\n\n\nvar<\/span> text = \"08:20 50:91 21:45 26:99\"<\/span>;\nvar<\/span> pattern = @\"([01][0-9]|2[0-3]):[0-5][0-9]\"<\/span>;\n\nvar<\/span> matches = Regex.Matches(text, pattern);\n\nforeach<\/span> (var<\/span> match in<\/span> matches)\n{\n    WriteLine(match);\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
It returns two matches corresponding to the valid time format hh:mm:<\/p>\n\n\n
08<\/span>\n21<\/span>:45<\/span><\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
The regular expression pattern [01]\\d|2[0-3]:[0-5]\\d<\/code> matches either a two-digit number starting with 0<\/code> or 1<\/code>, or a time in the format hh<\/code>:mm<\/code> between 20:00<\/code> and 23:59<\/code>.<\/p>\n\n\n\n
Let’s understand the regular expression ([01][0-9]|2[0-3]):[0-5][0-9]<\/code> step by step:<\/p>\n\n\n\n
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  • ([01][0-9]|2[0-3])<\/code> matches the hour portion of the time format. It contains two alternatives separated by the alternation operator (|<\/code>). The first alternative [01][0-9]<\/code> matches hours from 00<\/code> to 19<\/code>, representing the hours from 00<\/code> to 19<\/code>. The second alternative 2[0-3]<\/code> matches hours from 20<\/code> to 23<\/code>.<\/li>\n\n\n\n
  • :<\/code> matches the colon character, which separates the hour and minute portions of the time format.<\/li>\n\n\n\n
  • [0-5][0-9]<\/code> matches the minute portion of time from 00<\/code> to 59<\/code>.<\/li>\n<\/ul>\n\n\n\n
    Summary<\/h2>\n\n\n\n
      \n
    • Use regex alternation (|<\/code>) to match one pattern or another within the same regular expression.<\/li>\n<\/ul>\n
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