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Regex.Split Method (String, String, RegexOptions)

Splits an input string into an array of substrings at the positions defined by a specified regular expression pattern. Specified options modify the matching operation.

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

'Declaration
Public Shared Function Split ( _
	input As String, _
	pattern As String, _
	options As RegexOptions _
) As String()

Parameters

input
Type: System.String

The string to split.

pattern
Type: System.String

The regular expression pattern to match.

options
Type: System.Text.RegularExpressions.RegexOptions

A bitwise combination of the enumeration values that provide options for matching.

Return Value

Type: System.String()
An array of strings.

ExceptionCondition
ArgumentException

A regular expression parsing error occurred.

ArgumentNullException

input or pattern is Nothing.

ArgumentOutOfRangeException

options is not a valid bitwise combination of RegexOptions values.

RegexMatchTimeoutException

A time-out occurred. For more information about time-outs, see the Remarks section.

The Regex.Split methods are similar to the String.Split(Char()) method, except that Regex.Split splits the string at a delimiter determined by a regular expression instead of a set of characters. The string is split as many times as possible. If no delimiter is found, the return value contains one element whose value is the original input string.

The pattern parameter consists of 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.

Important noteImportant

Compiled regular expressions used in calls to static Split methods are automatically cached. To manage the lifetime of compiled regular expressions yourself, use the instance Split methods.

If multiple matches are adjacent to one another, an empty string is inserted into the array. For example, splitting a string on a single hyphen causes the returned array to include an empty string in the position where two adjacent hyphens are found.

If a match is found at the beginning or the end of the input string, an empty string is included at the beginning or the end of the returned array. The following example uses the regular expression pattern [a-z]+ to split an input string on any uppercase or lowercase alphabetic character. Because the string begins and ends with matching alphabetic characters, the value of the first and last element of the returned array is String.Empty.

Imports System.Text.RegularExpressions

Module Example
   Public Sub Main()
      Dim pattern As String = "[a-z]+" 
      Dim input As String = "Abc1234Def5678Ghi9012Jklm" 
      Dim result() As String = Regex.Split(input, pattern, 
                                           RegexOptions.IgnoreCase)
      For ctr As Integer = 0 To result.Length - 1
         Console.Write("'{0}'", result(ctr))
         If ctr < result.Length - 1 Then Console.Write(", ")
      Next
      Console.WriteLine()
   End Sub                
End Module 
' The example displays the following output: 
'       '', '1234', '5678', '9012', ''

If capturing parentheses are used in a Regex.Split expression, any captured text is included in the resulting string array. For example, if you split the string "plum-pear" on a hyphen placed within capturing parentheses, the returned array includes a string element that contains the hyphen.

Imports System.Text.RegularExpressions

Module Example
   Public Sub Main()
      Dim input As String = "plum-pear" 
      Dim pattern As String = "(-)"  

      Dim substrings() As String = Regex.Split(input, pattern)    ' Split on hyphens.
      For Each match As String In substrings
         Console.WriteLine("'{0}'", match)
      Next 
   End Sub 
End Module 
' The method writes the following to the console: 
'    'plum' 
'    '-' 
'    'pear'      

However, when the regular expression pattern includes multiple sets of capturing parentheses, the behavior of this method depends on the version of the .NET Framework. In the .NET Framework 1.0 and 1.1, if a match is not found within the first set of capturing parentheses, captured text from additional capturing parentheses is not included in the returned array. Starting with the .NET Framework 2.0, all captured text is also added to the returned array. For example, the following code uses two sets of capturing parentheses to extract the elements of a date, including the date delimiters, from a date string. The first set of capturing parentheses captures the hyphen, and the second set captures the forward slash. If the example code is compiled and run under the .NET Framework 1.0 or 1.1, it excludes the slash characters; if it is compiled and run under the .NET Framework 2.0 or later versions, it includes them.

Imports System
Imports System.Text.RegularExpressions

Module Example
   Public Sub Main()
      Dim input As String = "07/14/2007"    
      Dim pattern As String = "(-)|(/)" 
      For Each result As String In Regex.Split(input, pattern) 
         Console.WriteLine("'{0}'", result)
      Next 
   End Sub 
End Module 
' In .NET 1.0 and 1.1, the method returns an array of 
' 3 elements, as follows: 
'    '07' 
'    '14' 
'    '2007' 

' In .NET 2.0 and later, the method returns an array of 
' 5 elements, as follows: 
'    '07' 
'    '/' 
'    '14' 
'    '/' 
'    '2007' 

If the regular expression can match the empty string, Split will split the string into an array of single-character strings because the empty string delimiter can be found at every location.

The RegexMatchTimeoutException exception is thrown if the execution time of the split operation exceeds the time-out interval specified for the application domain in which the method is called. If no time-out is defined in the application domain's properties, or if the time-out value is Regex.InfiniteMatchTimeout, no exception is thrown.

Notes to Callers

This method times out after an interval that is equal to the default time-out value of the application domain in which the method is called. If a time-out value has not been defined for the application domain, the value InfiniteMatchTimeout, which prevents the method from timing out, is used. The recommended static method for splitting text on a pattern match is Regex.Split(String, String, RegexOptions, TimeSpan), which lets you set the time-out interval.

.NET Framework

Supported in: 4.5.2, 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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