using System;

using System.Linq;

using System.Text.RegularExpressions;

​

public class Program

{

    public static string LongestWord(string sen)

    {

        // Remove all non-alphanumeric characters and split the string into words

        string[] words = Regex.Replace(sen, @"[^a-zA-Z0-9\s]", "").Split(' ');

​

        // Find the longest word(s)

        var longestWords = from word in words

                           orderby word.Length descending

                           select word;

​

        // Return the first longest word

        return longestWords.First();

    }

​

    static void Main(string[] args)

    {

        Console.WriteLine(LongestWord("fun&!! time")); // Output: time

        Console.WriteLine(LongestWord("I love dogs")); // Output: love

    }

}

​