C# regular expressions

Regular expressions (regex) in C# provide a powerful and efficient way to search, replace, and validate strings. Regular expressions consist of a pattern, which is a sequence of characters that define a search pattern.

C# provides a dedicated namespace System.Text.RegularExpressions for working with regular expressions. The Regex class is used to create a regular expression object, which can then be used to match patterns against input strings.

Here is an example of using regular expressions in C# to match a pattern in a string:

using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main()
    {
        string input = "The quick brown fox jumps over the lazy dog.";

        // Define a regular expression pattern
        string pattern = @"\b\w{5}\b";

        // Create a regular expression object
        Regex regex = new Regex(pattern);

        // Find all matches
        MatchCollection matches = regex.Matches(input);

        // Print each match
        foreach (Match match in matches)
        {
            Console.WriteLine(match.Value);
        }
    }
}

In this example, the regular expression pattern \b\w{5}\b matches any word in the input string that is exactly 5 characters long. The \b character is a word boundary, and \w represents any word character (letters, digits, and underscores).

The Regex class provides many other methods for working with regular expressions, such as Match, Replace, Split, and more. Regular expressions can be complex, but with practice, they can be a powerful tool for string manipulation in C#.