Write C# method to reverse the input string without using String.Reverse() method

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace reverse_string
{
    class Program
    {
        static void Main(string[] args)
        {

            char[] a = new char[10];
            Console.WriteLine("enter a string(Max 10 char):");
            a = Console.ReadLine().ToCharArray();
            int len, i;
            char temp;
            len = a.Length - 1;
            for (i = 0; i < a.Length / 2; i++)
            {
                temp = a[i];
                a[i] = a[len];
                a[len--] = temp;
            }
            
            Console.WriteLine("the ordered array");
            for(i=0;i
                Console.Write(a[i]);
            Console.ReadKey();
        }
    }
}