Reverse A String In C#

using System;
class ReverseString {
    static void Main() {
        Console.WriteLine("Enter the String :");
        string a = Console.ReadLine();
        int len = a.Length;
        Console.Write("The Reverse of String is :");
        for (int i = len - 1; i >= 0; i--) {
            Console.Write(a[i]);
        }
        Console.WriteLine();
        Console.ReadKey();
    }
}