Postfix to Infix and showing steps to user

Question

Hello. I have to write a code where the user writes in postfix and the program transforms to infix. But that is not the problem, the problem is that in every step of this transformation I have to show in console app every step of this transformation, so I'm guessing what went out and what was left in the stack, but I don't know how to do this.  Please any help will be greatly appreciated and I will kiss your feet :D  Sorry for the broken English (Serbian).

 using System;
using System.Collections.Generic;

class Rpn
{
    public
 static void Main()
    {
        char[] sp = new char[] { ' ', 
'\t' };
        for (;; )
        {
            string s = 
Console.ReadLine();
            if (s == null) break;
            Stack<string>
 tks = new Stack<string>
                 (s.Split(sp, 
StringSplitOptions.RemoveEmpty
Entries));
            if 
(tks.Count == 0) continue;
            try
            {
                double
 r = evalrpn(tks);
                if (tks.Count != 0) throw new 
Exception();
                Console.WriteLine(r);
            }
            catch
 (Exception e) { Console.WriteLine("error"); }
        }
    }

    private
 static double evalrpn(Stack<string> tks)
    {
        string
 tk = tks.Pop();
        Console.WriteLine("sklad: " + tk);
        double
 x, y;
        if (!Double.TryParse(tk, out x))
        {
            y
 = evalrpn(tks); x = evalrpn(tks);
            if (tk == "+")
            {
                Console.WriteLine(x
 + " " + y);
                x += y;
            }
            else
 if (tk == "-")
            {
                Console.WriteLine(x +
 " " + y);
                x -= y;
            }
            else
 if (tk == "*")
            {
                Console.WriteLine(x +
 " " + y);
                x *= y;
            }
            else
 if (tk == "/")
            {
                Console.WriteLine(x +
 " " + y);
                x /= y;
            }
            else
 throw new Exception();
        }
        return x;
    }
}