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Regex.IsMatch Method (String, String)

Updated: September 2009

Indicates whether the regular expression finds a match in the input string using the regular expression specified in the pattern parameter.

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

public static bool IsMatch(
	string input,
	string pattern


Type: System.String

The string to search for a match.

Type: System.String

The regular expression pattern to match.

Return Value

Type: System.Boolean
true if the regular expression finds a match; otherwise, false.


A regular expression parsing error has occurred.


input is null.


pattern is null.

The IsMatch method is typically used to validate a string or to ensure that a string conforms to a particular pattern without retrieving that string for subsequent manipulation. To determine whether one or more strings match a regular expression pattern and to retrieve them for subsequent manipulation, call the Match or Matches method.

The static IsMatch(String, String) method is equivalent to constructing a Regex object with the regular expression pattern specified by pattern and calling the IsMatch(String) instance method. This regular expression pattern is cached for rapid retrieval by the regular expression engine.

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

The following example illustrates the use of the IsMatch(String, String) method to determine whether a string is a valid part number. The regular expression assumes that the part number has a specific format that consists of three sets of characters separated by hyphens. The first set, which contains four characters, must consist of an alphanumeric character followed by two numeric characters followed by an alphanumeric character. The second set, which consists of three characters, must be numeric. The third set, which consists of four characters, must have three numeric characters followed by an alphanumeric character.

using System;
using System.Text.RegularExpressions;

public class Example
   public static void Main()
      string[] partNumbers= { "1298-673-4192", "A08Z-931-468A", 
                              "_A90-123-129X", "12345-KKA-1230", 
                              "0919-2893-1256" };
      string pattern = @"^[a-zA-Z0-9]\d{2}[a-zA-Z0-9](-\d{3}){2}[A-Za-z0-9]$";
      foreach (string partNumber in partNumbers)
         Console.WriteLine("{0} {1} a valid part number.", 
                           Regex.IsMatch(partNumber, pattern) ? "is" : "is not");
// The example displays the following output: 
//       1298-673-4192 is a valid part number. 
//       A08Z-931-468A is a valid part number. 
//       _A90-123-129X is not a valid part number. 
//       12345-KKA-1230 is not a valid part number. 
//       0919-2893-1256 is not a valid part number.

The regular expression pattern is:


The following table shows how the regular expression pattern is interpreted.




Begin the match at the beginning of the line.


Match a single alphabetic character (a through z or A through Z) or numeric character.


Match two numeric characters.


Match a single alphabetic character (a through z or A through Z) or numeric character.


Match a hyphen.


Match exactly three numeric characters.


Find a hyphen followed by three numeric characters, and match two occurrences of this pattern.


Match a single alphabetic character (a through z or A through Z) or numeric character.


End the match at the end of the line.

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




September 2009

Modified the regular expression in the example.

Customer feedback.

March 2009

Updated exception information.

Customer feedback.

February 2009

Expanded the Remarks section and added an example.

Customer feedback.