1.) Match: The Match method is used to find the first occurrence of a pattern within a string. It returns a Match object that provides information about the match.

using System;
using System.Text.RegularExpressions;

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

        Match match = Regex.Match(text, pattern);

        if (match.Success)
        {
            Console.WriteLine("Match found at index " + match.Index);
        }
        else
        {
            Console.WriteLine("No match found.");
        }
    }
}

using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main()
    {
        string text = "The quick brown fox jumps over the lazy dog.";
        string pattern = @"\b\w{4}\b"; // Matches four-letter words

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

        foreach (Match match in matches)
        {
            Console.WriteLine("Match found: " + match.Value);
        }
    }
}

using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main()
    {
        string text = "The quick brown fox jumps over the lazy dog.";
        string pattern = @"\b\w{4}\b"; // Matches four-letter words
        string replacement = "****";

        string result = Regex.Replace(text, pattern, replacement);

        Console.WriteLine("Result: " + result);
    }
}

These are just a few examples of the operations you can perform with the Regex class. Regular expressions provide a powerful and flexible way to work with text patterns, and the Regex class in C# makes it easy to work with regular expressions in your code.