Groups Property
Collapse the table of content
Expand the table of content

Match.Groups Property

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Gets a collection of groups matched by the regular expression.

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

'Declaration
Public Overridable ReadOnly Property Groups As GroupCollection

Property Value

Type: System.Text.RegularExpressions.GroupCollection
The character groups matched by the pattern.

A regular expression pattern can include subexpressions, which are defined by enclosing a portion of the regular expression pattern in parentheses. Every such subexpression forms a group. For example, the regular expression pattern (\d{3})-(\d{3}-\d{4}), which matches North American telephone numbers, has two subexpressions. The first consists of the area code, which composes the first three digits of the telephone number. This group is captured by the first portion of the regular expression, (\d{3}).The second consists of the individual telephone number, which composes the last seven digits of the telephone number. This group is captured by the second portion of the regular expression, (\d{3}-\d{4}). These two groups can then be retrieved from the GroupCollection object that is returned by the Groups property, as the following example shows.


Imports System.Text.RegularExpressions

Module Example
   Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Dim pattern As String = "(\d{3})-(\d{3}-\d{4})"
      Dim input As String = "212-555-6666 906-932-1111 415-222-3333 425-888-9999"
      Dim matches As MatchCollection = Regex.Matches(input, pattern)

      For Each match As Match In matches
         outputBlock.Text += String.Format("Area Code:        {0}", match.Groups(1).Value) & vbCrLf
         outputBlock.Text += String.Format("Telephone number: {0}", match.Groups(2).Value) & vbCrLf
         outputBlock.Text &= vbCrLf
      Next
      outputBlock.Text &= vbCrLf
   End Sub
End Module
' The example displays the following output:
'       Area Code:        212
'       Telephone number: 555-6666
'       
'       Area Code:        906
'       Telephone number: 932-1111
'       
'       Area Code:        415
'       Telephone number: 222-3333
'       
'       Area Code:        425
'       Telephone number: 888-9999


The GroupCollection object returned by the Match.Groups property always has at least one member. If the regular expression engine cannot find any matches in a particular input string, the Group.Success property of the single Group object in the collection is set to False and the Group object's Value property is set to String.Empty. If the regular expression engine can find a match, the first element of the GroupCollection object returned by the Groups property contains a string that matches the entire regular expression pattern.

The following example attempts to match a regular expression pattern against a sample string. The example uses the Groups property to store information retrieved by the match for display to the console.


Imports System.Text.RegularExpressions
Module Example
   Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Dim text As String = "One car red car blue car"
      Dim pat As String = "(\w+)\s+(car)"

      ' Instantiate the regular expression object.
      Dim r As Regex = New Regex(pat, RegexOptions.IgnoreCase)

      ' Match the regular expression pattern against a text string.
      Dim m As Match = r.Match(text)
      Dim matchcount As Integer = 0
      Do While m.Success
         matchcount += 1
         outputBlock.Text += "Match" & (matchcount) & vbCrLf
         Dim i As Integer
         For i = 1 To 2
            Dim g As Group = m.Groups(i)
            outputBlock.Text += "Group" & i & "='" & g.ToString() & "'" & vbCrLf
            Dim cc As CaptureCollection = g.Captures
            Dim j As Integer
            For j = 0 To cc.Count - 1
               Dim c As Capture = cc(j)
               outputBlock.Text += "Capture" & j & "='" & c.ToString() _
                  & "', Position=" & c.Index & vbCrLf
            Next 
         Next 
         m = m.NextMatch()
      Loop
   End Sub
End Module
' This example displays the following output:
'       Match1
'       Group1='One'
'       Capture0='One', Position=0
'       Group2='car'
'       Capture0='car', Position=4
'       Match2
'       Group1='red'
'       Capture0='red', Position=8
'       Group2='car'
'       Capture0='car', Position=12
'       Match3
'       Group1='blue'
'       Capture0='blue', Position=16
'       Group2='car'
'       Capture0='car', Position=21


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

Show:
© 2017 Microsoft