GroupCollection Class

The GroupCollection class consists of one or more Group objects that provide information about captured groups in a regular expression match. 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 Group object that corresponds to the entire match. Each subsequent element represents a captured group, if the regular expression includes capturing groups. Matches from numbered (unnamed) capturing groups appear in numeric order before matches from named capturing groups. If the match is unsuccessful, the collection contains a single System.Text.RegularExpressions.Group object whose Success property is false and whose Value property equals String.Empty. For more information, see the "Grouping Constructs and Regular Expression Objects" section in the Grouping Constructs in Regular Expressions article.

To iterate through the members of the collection, you should use the collection iteration construct provided by your language (such as foreach in C# and For Each…Next in Visual Basic) instead of retrieving the enumerator that is returned by the GetEnumerator method.

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.

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

using System;
using System.Text.RegularExpressions;

public class Example
{
   public static void Main()
   {
      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;
         Console.WriteLine("{0}: {1}", groups[2], groups[1]);
      }                               
      Console.WriteLine();
      Console.WriteLine("Found {0} trademarks or registered trademarks.", matches.Count);
   }
}
// The example displays the following output: 
//       r: Microsoft 
//       r: Excel 
//       r: Access 
//       r: Outlook 
//       r: PowerPoint 
//       T: Silverlight

.NET Framework

.NET Framework Client Profile

Portable Class Library

.NET for Windows Store apps

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.

Reference