Article
11/18/2011

GroupCollection Class

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Updated: August 2009

Represents a collection of captured groups in a single match.

Inheritance Hierarchy

System.Object
System.Text.RegularExpressions.GroupCollection

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

Syntax

'Declaration
<DefaultMemberAttribute("Item")> _
Public Class GroupCollection _
    Implements ICollection, IEnumerable

[DefaultMemberAttribute("Item")]
public class GroupCollection : ICollection, 
    IEnumerable

The GroupCollection type exposes the following members.

Properties

	Name	Description
	Count	Returns the number of groups in the collection.
	IsReadOnly	Gets a value that indicates whether the collection is read-only.
	IsSynchronized	Gets a value that indicates whether access to the GroupCollection is synchronized (thread-safe).
	Item[Int32]	Enables access to a member of the collection by integer index.
	Item[String]	Enables access to a member of the collection by string index.
	SyncRoot	Gets an object that can be used to synchronize access to the GroupCollection.

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Methods

	Name	Description
	CopyTo	Copies all the elements of the collection to the given array beginning at the given index.
	Equals(Object)	Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetEnumerator	Returns an enumerator that can iterate through the collection.
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	ToString	Returns a string that represents the current object. (Inherited from Object.)

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Extension Methods

	Name	Description
	AsQueryable	Converts an IEnumerable to an IQueryable. (Defined by Queryable.)
	Cast<TResult>	Converts the elements of an IEnumerable to the specified type. (Defined by Enumerable.)
	OfType<TResult>	Filters the elements of an IEnumerable based on a specified type. (Defined by Enumerable.)

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Remarks

The collection is immutable (read-only) and has no public constructor. A GroupCollection object is returned by the Match.Groups property.

The collection contains one or more System.Text.RegularExpressions.Group objects. If the match is successful, the first element in the collection contains the string that corresponds to the entire match. Each subsequent element represents a captured group, if the regular expression includes capturing groups. If the match is unsuccessful, the collection contains a single element whose Success property is false and whose Value property equals String.Empty.

Examples

The following example uses a regular expression with capturing groups to extract information about trademarks and registered trademarks used in text. The regular expression pattern is \b(\w+?)([\u00AE\u2122]), which is interpreted as shown in the following table.

Pattern	Description
\b	Look for a word boundary.
(\w+?)	Look for one or more word characters. Together, these characters form the trademarked name. (Note that this regular expression assumes that a trademark consists of a single word.) This is the first capturing group.
([\u00AE\u2122])	Look for either the ® or the ™ character. This is the second capturing group.

For each match, the GroupCollection object contains three Group objects. The first contains the string that matches the entire regular expression. The second, which represents the first captured group, contains the product name. The third, which represents the second captured group, contains the trademark or registered trademark symbol.

Imports System.Text.RegularExpressions

Module Example
   Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Dim pattern As String = "\b(\w+?)([\u00AE\u2122])"
      Dim input As String = "Microsoft® Office Professional Edition combines several office " + _
                            "productivity products, including Word, Excel®, Access®, Outlook®, " + _
                            "PowerPoint®, and several others. Some guidelines for creating " + _
                            "corporate documents using these productivity tools are available " + _
                            "from the documents created using Silverlight™ on the corporate " + _
                            "intranet site."

      Dim matches As MatchCollection = Regex.Matches(input, pattern)
      For Each match As Match In matches
         Dim groups As GroupCollection = match.Groups
         outputBlock.Text += String.Format("{0}: {1}", groups(2), groups(1)) & vbCrLf
      Next
      outputBlock.Text += vbCrLf
      outputBlock.Text += String.Format("Found {0} trademarks or registered trademarks.", matches.Count) & vbCrLf
   End Sub
End Module
' The example displays the following output:
'       ®: Microsoft
'       ®: Excel
'       ®: Access
'       ®: Outlook
'       ®: PowerPoint
'       ™: Silverlight

using System;
using System.Text.RegularExpressions;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      string pattern = @"\b(\w+?)([\u00AE\u2122])";
      string input = "Microsoft® Office Professional Edition combines several office " +
                     "productivity products, including Word, Excel®, Access®, Outlook®, " +
                     "PowerPoint®, and several others. Some guidelines for creating " +
                     "corporate documents using these productivity tools are available " +
                     "from the documents created using Silverlight™ on the corporate " +
                     "intranet site.";

      MatchCollection matches = Regex.Matches(input, pattern);
      foreach (Match match in matches)
      {
         GroupCollection groups = match.Groups;
         outputBlock.Text += String.Format("{0}: {1}", groups[2], groups[1]) + "\n";
      }
      outputBlock.Text += "\n";
      outputBlock.Text += String.Format("Found {0} trademarks or registered trademarks.", matches.Count) + "\n";
   }
}
// The example displays the following output:
//       ®: Microsoft
//       ®: Excel
//       ®: Access
//       ®: Outlook
//       ®: PowerPoint
//       ™: Silverlight

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Change History

Date	History	Reason
August 2009	Expanded the Remarks section.	Customer feedback.

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