可以在.net中扩展String类

public static class StringExtensions
{
    public static string Reverse(this string input)
    {
        char[] charArray = input.ToCharArray();
        Array.Reverse(charArray);
        return new string(charArray);
    }
}

using System;

namespace ExtensionMethods
{
    class Program
    {
        static void Main(string[] args)
        {
            string myString = "Hello, World!";
            string reversedString = myString.Reverse();
            Console.WriteLine(reversedString);
        }
    }
}