Match.Groups Property


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Gets a collection of groups matched by the regular expression.

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

public virtual GroupCollection Groups { get; }

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. The Groups property provides access to information about those subexpression matches. 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.

using System;
using System.Text.RegularExpressions;

public class Example
   public static void Main()
      string pattern = @"(\d{3})-(\d{3}-\d{4})";
      string input = "212-555-6666 906-932-1111 415-222-3333 425-888-9999";
      MatchCollection matches = Regex.Matches(input, pattern);

      foreach (Match match in matches)
         Console.WriteLine("Area Code:        {0}", match.Groups[1].Value);
         Console.WriteLine("Telephone number: {0}", match.Groups[2].Value);
// 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 is a zero-based collection object that 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 (the object at index 0) 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 (the element at index 0) returned by the Groups property contains a string that matches the entire regular expression pattern. Each subsequent element, from index one upward, represents a captured group, if the regular expression includes capturing groups. For more information, see the "Grouping Constructs and Regular Expression Objects" section of the Grouping Constructs in Regular Expressions article.

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

using System;
using System.Text.RegularExpressions;

class Example 
   static void Main() 
      string text = "One car red car blue car";
      string pat = @"(\w+)\s+(car)";

      // Instantiate the regular expression object.
      Regex r = new Regex(pat, RegexOptions.IgnoreCase);

      // Match the regular expression pattern against a text string.
      Match m = r.Match(text);
      int matchCount = 0;
      while (m.Success) 
         Console.WriteLine("Match"+ (++matchCount));
         for (int i = 1; i <= 2; i++) 
            Group g = m.Groups[i];
            Console.WriteLine("Group"+i+"='" + g + "'");
            CaptureCollection cc = g.Captures;
            for (int j = 0; j < cc.Count; j++) 
               Capture c = cc[j];
               System.Console.WriteLine("Capture"+j+"='" + c + "', Position="+c.Index);
         m = m.NextMatch();
// 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

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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