static void Main(string[] args)
{
    string Str,  Revstr = " "; 
    int Length;
    Console.Write("Enter A String : ");
    Str = Console.ReadLine();
    Length = Str.Length - 1;
    while (Length >= 0)
    {
        Revstr = Revstr + Str[Length];
        Length --;
    }
    Console.WriteLine("Reverse  String  Is  {0}",  Revstr);
    Console.ReadLine();
}