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Regex.Match Method (String, Int32)

Updated: July 2009

Searches the input string for the first occurrence of a regular expression, beginning at the specified starting position in the string.

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

public Match Match(
	string input,
	int startat
)

Parameters

input
Type: System.String

The string to search for a match.

startat
Type: System.Int32

The zero-based character position at which to start the search.

Return Value

Type: System.Text.RegularExpressions.Match
An object that contains information about the match.

ExceptionCondition
ArgumentNullException

input is null.

ArgumentOutOfRangeException

startat is less than zero or greater than the length of input.

The regular expression pattern for which the Regex.Match(String, Int32) method searches is defined by the call to one of the Regex class constructors. For more information about the elements that can form a regular expression pattern, see Regular Expression Language - Quick Reference.

You can optionally specify a starting position in the string by using the startat parameter. When the regular expression engine parses from left-to-right (the default), the match and the scan proceed rightward, starting at the character specified in startat. When the regular expression engine parses from right-to-left (when the regular expression pattern is constructed with the RegexOptions.RightToLeft option), the match and scan proceed in the opposite direction and begin with the character at startat -1. If you do not specify a starting position, the search begins at the default startat position. If the regular expression searches from left to right, the default startat position is at the left end of input; if it searches from right to left, the default startat position is at the right end of input.

If you want to restrict a match so that it begins at a particular character position in the string and the regular expression engine does not scan the remainder of the string for a match, anchor the regular expression with a \G (at the left for a left-to-right pattern, or at the right for a right-to-left pattern). This restricts the match so it must start exactly at startat.

You can determine whether the regular expression pattern has been found in the input string by checking the value of the returned Match object's Success property. If a match is successful, the returned Match object's Value property contains the substring from input that matches the regular expression pattern. If no match is found, its value is String.Empty.

This method returns the first substring found at or after the startat character position in input that matches the regular expression pattern. You can retrieve subsequent matches by repeatedly calling the returned Match object's NextMatch method. You can also retrieve all matches in a single method call by calling the Regex.Matches(String, Int32) method.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

Date

History

Reason

July 2009

Included additional exception information.

Content bug fix.

March 2009

Expanded the Remarks section.

Customer feedback.

October 2008

Expanded the Remarks section.

Customer feedback.

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