using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string old_str = @"<span style=""font-weight:underline;"">John</span> <span style=""font-style: underline;"">Steve</span> <span style=""text-decoration: underline;"">Abrahem</span>";

        string new_str = Regex.Replace(old_str, "<.*?>(.*?)<.*?>", new MatchEvaluator(Replace));

        Console.WriteLine(new_str);

    }

    static string Replace(Match m)

    {

        return "<ul>" + m.Groups[1] + "</ul>";

    }

}