public static class StringExtension
{
    public static string Reverse(this string s)
    {
        List<string> characters = s.Select(c => c.ToString()).ToList();

        characters.Reverse();

        return string.Join("", characters.ToArray());
    }

    public static bool IsNumeric(this string s)
    {
        double output;

        return double.TryParse(s, out output);
    }

    public static string ToRocDateString(this DateTime date, char separator)
        => $"{(date.Year - 1911)}{separator}{date.Month}{separator}{date.Day}";

    public static string GetName(this Account account)
        => account.Name;
}

public class Account
{
    public string Name { get; set; }
}

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("123456789".Reverse());

        Console.WriteLine("100".IsNumeric());

        Console.WriteLine(DateTime.Now.ToRocDateString('/'));

        Account account = new Account { Name = "Joey" };

        Console.WriteLine(account.GetName());

        Console.ReadKey();
    }
}