What are regular expression Balancing Groups in C#?

What are regular expression Balancing Groups in C#?

Balancing groups in C# regular expressions are a feature that allows you to keep track of nested patterns or matched groups that occur in pairs. They are used to match patterns that have a balanced structure, such as nested parentheses, tags, or brackets.

In C# regular expressions, balancing groups are represented by the (?<group1-group2>) syntax, where group1 and group2 are the two named capturing groups that are being balanced. The group1 and group2 names can be any valid capturing group names. The group1 group represents the opening delimiter of the balanced pattern, while the group2 group represents the closing delimiter.

Here's an example of how to use balancing groups in a regular expression to match nested parentheses:

string input = "(a(b)c)d(e(f)g)h";
string pattern = @"\((?<content>[^()]*(\g<content>[^()]*)*)\)";

MatchCollection matches = Regex.Matches(input, pattern);

foreach (Match match in matches)
{
    Console.WriteLine("Match: " + match.Value);
    Console.WriteLine("Content: " + match.Groups["content"].Value);
}

In this example, the input string contains nested parentheses that need to be matched. The pattern regular expression uses a balancing group named content to match the content inside the nested parentheses. The content group matches any sequence of characters that are not parentheses, as well as any nested parentheses that occur in pairs. The (\g<content>[^()]*)* subpattern is used to match any number of nested pairs of parentheses inside the content group.

When the regular expression is applied to the input string using the Regex.Matches method, it returns a collection of matches that correspond to the nested parentheses. Each match has a Value property that contains the entire matched substring, and a Groups["content"].Value property that contains the content inside the nested parentheses.

Note that balancing groups can also be used to match other types of balanced structures, such as HTML tags, XML elements, or JSON objects. They are a powerful and flexible feature of C# regular expressions that can greatly simplify pattern matching and text processing tasks.

Examples

  1. "C# regex balancing groups example" Description: Learn about balancing groups in regular expressions in C# for advanced pattern matching.

    using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main(string[] args)
    {
        string input = "((()))";

        string pattern = @"
            \(
            (?<depth>)
            |
            (?<-depth>)
            |
            (?(depth)(?!))
        ";

        MatchCollection matches = Regex.Matches(input, pattern, RegexOptions.IgnorePatternWhitespace);
        foreach (Match match in matches)
        {
            Console.WriteLine(match.Value);
        }
    }
}

  2. "C# regex balancing groups syntax" Description: Understand the syntax of balancing groups in regular expressions in C# for capturing matched groups.

    using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main(string[] args)
    {
        string input = "((()))";

        string pattern = @"
            \(
            (?<depth>)
            |
            (?<-depth>)
            |
            (?(depth)(?!))
        ";

        MatchCollection matches = Regex.Matches(input, pattern, RegexOptions.IgnorePatternWhitespace);
        foreach (Match match in matches)
        {
            Console.WriteLine(match.Value);
        }
    }
}

  3. "C# regex balancing groups nested parentheses" Description: Explore how to use balancing groups in regular expressions in C# to match nested parentheses.

    using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main(string[] args)
    {
        string input = "((()))";

        string pattern = @"
            \(
            (?<depth>)
            |
            (?<-depth>)
            |
            (?(depth)(?!))
        ";

        MatchCollection matches = Regex.Matches(input, pattern, RegexOptions.IgnorePatternWhitespace);
        foreach (Match match in matches)
        {
            Console.WriteLine(match.Value);
        }
    }
}

  4. "C# regex balancing groups nested brackets" Description: Learn how to use balancing groups in regular expressions in C# to match nested brackets.

    using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main(string[] args)
    {
        string input = "[[[][]]]";

        string pattern = @"
            \[
            (?<depth>)
            |
            (?<-depth>)
            |
            (?(depth)(?!))
        ";

        MatchCollection matches = Regex.Matches(input, pattern, RegexOptions.IgnorePatternWhitespace);
        foreach (Match match in matches)
        {
            Console.WriteLine(match.Value);
        }
    }
}

  5. "C# regex balancing groups curly braces" Description: Explore how to use balancing groups in regular expressions in C# to match nested curly braces.

    using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main(string[] args)
    {
        string input = "{{{}}}";

        string pattern = @"
            \{
            (?<depth>)
            |
            (?<-depth>)
            |
            (?(depth)(?!))
        ";

        MatchCollection matches = Regex.Matches(input, pattern, RegexOptions.IgnorePatternWhitespace);
        foreach (Match match in matches)
        {
            Console.WriteLine(match.Value);
        }
    }
}

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