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Regex Constructor (String, RegexOptions)

Initializes a new instance of the Regex class for the specified regular expression, with options that modify the pattern.

Namespace:  System.Text.RegularExpressions
Assembly:  System (in System.dll)
public Regex(
	string pattern,
	RegexOptions options
)

Parameters

pattern
Type: System.String

The regular expression pattern to match.

options
Type: System.Text.RegularExpressions.RegexOptions

A bitwise combination of the enumeration values that modify the regular expression.

ExceptionCondition
ArgumentException

A regular expression parsing error occurred.

ArgumentNullException

pattern is null.

ArgumentOutOfRangeException

options contains an invalid flag.

The pattern parameter consists of 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 - Quick Reference topics.

A Regex object is immutable, which means that it can be used only for the match parameters you define when you create it. However, it can be used any number of times without being recompiled.

Notes to Callers

This constructor creates a Regex object that uses the default time-out value of the application domain in which it is created. If a time-out value has not been defined for the application domain, the Regex object uses the value InfiniteMatchTimeout, which prevents the operation from timing out. The recommended constructor for creating a Regex object is Regex.Regex(String, RegexOptions, TimeSpan), which lets you set the time-out interval.

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".

string pattern = @"\b[at]\w+";
RegexOptions options = RegexOptions.IgnoreCase | RegexOptions.Compiled;
string text = "The threaded application ate up the thread pool as it executed.";
MatchCollection matches;

Regex optionRegex = new Regex(pattern, options);
Console.WriteLine("Parsing '{0}' with options {1}:", text, options.ToString());
// Get matches of pattern in text
matches = optionRegex.Matches(text);
// Iterate matches 
for (int ctr = 0; ctr < matches.Count; ctr++)
   Console.WriteLine("{0}. {1}", ctr, matches[ctr].Value);

Note that the match collection includes the word "The" that begins the text because the options parameter has defined case-insensitive comparisons.

.NET Framework

Supported in: 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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