using System;

using System.Text;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var str = "Hello World!";

        char[] arr = null; //Broken out for documentation only.

        //Note the need to convert to a char array isn't really there. I am doing this for code clarity.        

        arr = str.ToCharArray(); 

        NormalWay(arr);

​

        arr = str.ToCharArray(); //Reset Data

        ForLoop(arr);

        arr = str.ToCharArray(); //Reset Data

        ForEachStack(arr);

    }

    private static void NormalWay(char[] data){

        Console.WriteLine("\nNormal Way.");

        Array.Reverse(data);

        Console.WriteLine(data);

    }

    private static void ForLoop(char[] data){

        Console.WriteLine("\nUsing String Builder and a for loop.");

        var sb = new StringBuilder();

        for(var i = data.Length - 1 ; i >= 0 ; i--)

        {

            sb.Append(data[i]);

​

        }

        Console.WriteLine(sb.ToString());

    }

    private static void ForEachStack(char[] data){

        Console.WriteLine("\nUsing a stack and a foreach loop.");

        var stk = new Stack<char>();

        foreach(var n in data)

            stk.Push(n);

        Console.WriteLine(stk.ToArray());

    }

}