Reverses a string.

Use string.ToCharArray() to convert the string to an array of char, Array.Reverse() to reverse the array.
Use IEnumerable.ToArray() to create an array of char and pass it to a new string().


using System.Linq;

public static partial class _30s 
  public static void Reverse(string s) 
    return new string(s.ToCharArray().Reverse().ToArray());


string s = "Hello World";

_30s.Reverse(s); // "dlroW olleH"