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Regex.IsMatch Method (String)

Indicates whether the regular expression specified in the Regex constructor finds a match in a specified input string.

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

public bool IsMatch(
	string input
)

Parameters

input
Type: System.String
The string to search for a match.

Return Value

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

ExceptionCondition
ArgumentNullException

input 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 following example illustrates the use of the IsMatch(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" };
      Regex rgx = new Regex(@"^[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.", 
                           partNumber, 
                           rgx.IsMatch(partNumber) ? "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:

^[a-zA-Z0-9]\d{2}[a-zA-Z0-9](-\d{3}){2}[A-Za-z0-9]$

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

Pattern

Description

^

Begin the match at the beginning of the line.

[a-zA-Z0-9]

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

\d{2}

Match two numeric characters.

[a-zA-Z0-9]

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

-

Match a hyphen.

\d{3}

Match exactly three numeric characters.

(-\d{3}){2}

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

[a-zA-Z0-9]

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

$

End the match at the end of the line.

.NET Framework

Supported in: 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

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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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