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GroupCollection::Item Property (String)

Enables access to a member of the collection by string index.

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

public:
property Group^ Item[String^ groupname] {
	Group^ get (String^ groupname);
}

Parameters

groupname
Type: System::String

The name of a capturing group.

Property Value

Type: System.Text.RegularExpressions::Group
The member of the collection specified by groupname.

groupName can be either the name of a capturing group that is defined by the (?<name>) element in a regular expression, or the string representation of the number of a capturing group that is defined by a grouping construct. For more information about groups in regular expressions, see Grouping Constructs in Regular Expressions.

You can retrieve the names of all the captured groups in a Regex object by calling the Regex::GetGroupNames method. You can also map the numbers of capturing groups in a regular expression to their names by calling the Regex::GroupNameFromNumber method. Individual names from the array can then be passed to the Item[String] property to retrieve the captured string.

If groupname is not the name of a capturing group in the collection, or if groupname is the name of a capturing group that has not been matched in the input string, the method returns a Group object whose Group::Success property is false and whose Group.Value property is String::Empty.

The following example defines a regular expression that consists of two named groups. The first group, numbers, captures one or more consecutive digits. The second group, letter, matches a single character. Because the regular expression engine looks for zero or one occurrence of the pattern defined by the numbers group, the numbers group is not always present even if a match is successful. The example then illustrates the result when the Item[String] property is used to retrieve an unmatched group, a matched group, and a group that is not defined in the regular expression. The example defines a regular expression pattern (?<numbers>\d+)*(?<letter>\w)\k<letter>, which is interpreted as shown in the following table.

Pattern

Description

(?<numbers>\d+)*

Match one or more occurrence of a decimal digit. Name this the numbers capturing group. Match this pattern either zero or one time.

(?<letter>\w)

Match a single word character. Name this the letter capturing group.

\k<letter>

Match the string captured by the letter capturing group.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8
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