Solution Review: Evaluate Postfix Expression Using a Stack

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace chapter_4
{
    class Challenge_6
    {
        static int evaluatePostFix(string exp)
        {
            Stack<int> stack = new Stack<int>();
            char character;
            int x, y;
            //1.Scan expression character by character,
            //2.If character is a number push it in stack
            //3.If character is operator then pop two elements from stack
            //perform the operation and put the result back in stack
            //At the end, Stack will contain result of whole expression.
            for (int i = 0; i < exp.Length; i++)
            {
                character = exp[i];
                if (!Char.IsDigit(character))
                {
                    x = stack.Pop();
                    y = stack.Pop();
                    switch (character)
                    {
                        case '+':
                            stack.Push(y + x);
                            break;
                        case '-':
                            stack.Push(y - x);
                            break;
                        case '*':
                            stack.Push(y * x);
                            break;
                        case '/':
                            stack.Push(y / x);
                            break;
                    }
                }
                else
                    stack.Push(character - '0');
            }
            return stack.Pop();
        }
        static void Main(string[] args)
        {
            Console.WriteLine(evaluatePostFix("921*-8-4+"));
        }
    }
}