This documentation is archived and is not being maintained.

Regex.Regex(String) Constructor

Initializes and compiles a new instance of the Regex class for the specified regular expression.

Namespace: System.Text.RegularExpressions
Assembly: System (in system.dll)

public Regex (
	string pattern
public Regex (
	String pattern
public function Regex (
	pattern : String
Not applicable.



The regular expression pattern to match.

Exception typeCondition


Regular expression parsing error.

The pattern parameter consists of various regular expression language elements that symbolically describe the string to match. For more information about regular expressions, see the .NET Framework Regular Expressions and Regular Expression Language Elements topics.

A Regex object is immutable, which means that it can be used only for the match parameters defined when it is created. It can be used any number of times without being recompiled, however.

This constructor instantiates a regular expression object that performs a case-sensitive match of any alphabetic characters defined in pattern. For a case-insensitive match, use the System.Text.RegularExpressions.Regex(String,RegexOptions) constructor.

The following example illustrates how to use this constructor to instantiate a regular expression that matches any word that begins with the letters "a" or "t".

Note that, because comparisons are case-sensitive by default, the regular expression pattern fails to match the word "The" at the beginning of the text.

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0