Regex.IsMatch Method (String) (System.Text.RegularExpressions)

.NET Framework Class Library

Regex..::.IsMatch Method (String)

Updated: February 2009

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

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

Syntax

Visual Basic (Declaration)

Public Function IsMatch ( _
    input As String _
) As Boolean

Visual Basic (Usage)

Dim instance As Regex
Dim input As String
Dim returnValue As Boolean

returnValue = instance.IsMatch(input)

public bool IsMatch(
    string input
)

Visual C++

public:
bool IsMatch(
    String^ input
)

JScript

public function IsMatch(
    input : String
) : boolean

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.

Exceptions

Exception	Condition
ArgumentNullException	input is nullNothingnullptra null reference (Nothing in Visual Basic).

Remarks

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.

Examples

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.

Visual Basic

Imports System.Text.RegularExpressions

Module Example
   Public Sub Main()
      Dim partNumbers() As String = { "1298-673-4192", "A08Z-931-468A", _
                                      "_A90-123-129X", "12345-KKA-1230", _
                                      "0919-2893-1256" }
      Dim rgx As New Regex("[a-zA-Z0-9]\d{2}[a-zA-Z0-9](-\d{3}){2}[A-Za-z0-9]")
      For Each partNumber As String In partNumbers
         Console.WriteLine("{0} {1} a valid part number.", _
                           partNumber, _
                           IIF(rgx.IsMatch(partNumber), "is", "is not"))
      Next
   End Sub
End Module
' 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.

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
[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.

Platforms

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.

Version Information