It's best practice to escape square brackets ( ) when they appear as literals in a char class.It's usually just best to escape them anyway. In those flavors, no additional escaping is necessary. Some flavors only use ^ and $ as metacharacters when they are at the start or end of the regex respectively.In order to use a literal ^ at the start or a literal $ at the end of a regex, the character must be escaped.
There are several characters that need to be escaped to be taken literally (at least outside char classes): In order to use a literal backslash anywhere in a regex, it must be escaped by another backslash. literal status of the character in front of it. Backslash escapes and backslash brings it actually toggles on or off the metacharacter vs. Saying that backslash is the "escape" character is a bit misleading. Escaping depends on context, therefore this example does not cover string or delimiter escaping. Use the methods of the System.Character escaping is what allows certain characters (reserved by the regex engine for manipulating searches) to be literally searched for and found in the input string. For example, the String.Contains, String.EndsWith, and String.StartsWith methods determine whether a string instance contains a specified substring and the String.IndexOf, String.IndexOfAny, String.LastIndexOf, and String.LastIndexOfAny methods return the starting position of a specified substring in a string. The System.String class includes several search and comparison methods that you can use to perform pattern matching with text.
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There are also a number of online libraries of regular expression patterns, such as the one at .įor more information about using the Regex class, see the following sections in this topic:įor more information about the regular expression language, see Regular Expression Language - Quick Reference or download and print one of these brochures: It can be used to quickly parse large amounts of text to find specific character patterns to extract, edit, replace, or delete text substrings and to add the extracted strings to a collection to generate a report.įor some common regular expression patterns, see Regular Expression Examples. NET Framework's regular expression engine. To prevent any misinterpretation, the example passes each dynamically generated string to the Escape method.
' The example displays the following output:īecause the regular expression in this example is built dynamically, we do not know at design time whether the current culture's currency symbol, decimal sign, or positive and negative signs might be misinterpreted by the regular expression engine as regular expression language operators. MatchCollection^ matches = rx->Matches( text ) Ĭonsole::WriteLine( " is not a currency value.", test) String^ text = "The the quick brown fox fox jumps over the lazy dog dog." Regex^ rx = gcnew Regex( "\\b(?\\w+)\\s+(\\k)\\b",static_cast(RegexOptions::Compiled | RegexOptions::IgnoreCase) ) Define a regular expression for repeated words. Using namespace System::Text::RegularExpressions Match the captured group that is named word. Match one or more white-space characters. Match one or more word characters up to a word boundary. The regular expression \b(?\w+)\s+(\k)\b can be interpreted as shown in the following table. The following example uses a regular expression to check for repeated occurrences of words in a string.
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