trees with reverse polish notation, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Microsoft (R) Visual C# Compiler version 2.9.0.63208 (958f2354)

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

namespace Rextester
    
{
    class Node
    {
      public int id;public int data = 0;
      public Node a = null,b = null;
      public Node(int ID){id = ID;}
      public Node(int ID, int Data){id = ID; data = Data;}
      
      public int sum()
      {
        if (a == null || b == null || id == 0) {return data;}
      
        switch(id)
        {
          case 1:
            return a.sum() + b.sum();
          case 2:
            return a.sum() - b.sum();
          case 3:
            return a.sum() * b.sum();
        }
        return 0;
      }
        public override string ToString() => id == 0? data.ToString(): $"{(a.id != 0 ? "(":"")}{a.ToString()}{(a.id != 0 ? ")":"")} {(id == 1 ? "+":(id == 2 ? "-":"*"))} {(b.id != 0 ? "(":"")}{b.ToString()}{(b.id != 0 ? ")":"")}";
    }
    
    
    
    public class Program
    {
        static Node NodeParse(string txt)
        {
            //nums and operator
            string nums = txt.Split('|')[0];
            string operators = txt.Split('|')[1];
            //parsing given values
            Stack<int> values = new Stack<int>();
            foreach(string val in nums.Split(',')){values.Push(int.Parse(val));}
            //variables for parsing
            Stack<Node> temps = new Stack<Node>();
            
            //parsing
            foreach(char oper in operators.ToCharArray())
            {
                Node temp = new Node("+-*".IndexOf(oper)+1);
                switch (values.Count)
                {
                    default:
                        temp.a = new Node(0,values.Pop());
                        temp.b = new Node(0,values.Pop());
                        break;
                        
                    case 1:
                        temp.a = new Node(0,values.Pop());
                        temp.b = temps.Pop();
                        break;
                    case 0:
                        temp.a = temps.Pop();
                        temp.b = temps.Pop();
                        break;
                        
                }
                temps.Push(temp);
            }
            //returning
            return temps.Pop();
        }
        public static void Main (string[] args) 
        {    /*
            Node root = new Node(1);
            root.a = new Node(0,2); root.b = new Node(3);
            root.b.a = new Node(0,3); root.b.b = new Node(0,2);
            */
            string reversePolish = Console.ReadLine();// "2,3|-";
            reversePolish = "10,3,4|*+"; //comment out this line for readline to work
            Node root = NodeParse(reversePolish);
            Console.WriteLine ($"{reversePolish} => {root.ToString()} = {root.sum()}");
            
      }
    }
}

Show compiler warnings [ - ] Show input
Compilation time: 0,22 sec, absolute running time: 0,11 sec, cpu time: 0,11 sec, average memory usage: 15 Mb, average nr of threads: 3, absolute service time: 0,34 sec