Math praser

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data;

namespace calcu
{
    class Program
    {
        // Function to transform an infix expression to its postfix form.
        static string InfixPostfix(string infix)
        {
            string postfix = "";
            Stack<char> opers = new Stack<char>();
            if(infix[0] == '-')
            {
                infix = "0" + infix;
            }
            for (int i = 0; i < infix.Length; i++)
            {
                if (infix[i] == ' ') { continue; }
                if (!"+*/-()".Contains(infix[i]))
                {
                    postfix += infix[i];
                }
                else if ("+*/-".Contains(infix[i]))
                {
                    postfix += ' ';
                    while ((opers.Count != 0) && opers.Peek() != '(' && IsFirstStronger(opers.Peek(), infix[i]))
                    {
                        postfix += opers.Pop();
                        postfix += ' ';
                    }
                    opers.Push(infix[i]);
                }
                else if (infix[i] == '(')
                {
                    opers.Push('(');
                }
                else if(infix[i] == ')')
                {
                    while(opers.Count()!= 0 && opers.Peek() != '(')
                    {
                        postfix += ' ';
                        postfix += opers.Pop();

                    }
                    opers.Pop();
                }
            }
            while (opers.Count != 0)
            {
                postfix += ' ';
                postfix += opers.Pop();
            }

            return postfix;
        }
        // Function to compare the precedence of two operators giving as input
        // and returns true if the first has higher order than the second.
        static bool IsFirstStronger(char nibber1, char nibber2)
        {
            Dictionary<char, int> d = new Dictionary<char, int>()
            {
                {'*', 2},
                {'/', 2},
                {'+', 1},
                {'-', 1}
            };
            if (d[nibber1] == d[nibber2])
            {
                return true;
            }
            return d[nibber1] > d[nibber2];
        }
        // Function to evaluate a postfix expression.
        static float EvaluatePostfix(string postfix)
        {
            float result = 0f;
            List<string> expression = new List<string>();
            expression = postfix.Split(' ').ToList();
            string temp = "";
            Stack<string> oprand = new Stack<string>();
            foreach (string ele in expression)
            {
                if (!"+-/*".Contains(ele))
                {
                    oprand.Push(ele);
                }
                else if ("+-/*".Contains(ele))
                {
                    oprand.Push(Compute(oprand.Pop(), oprand.Pop(), ele[0]).ToString());
                }
            }
            return float.Parse(oprand.Pop());
        }
        static float Compute(string num2, string num1, char oper)
        {
            float intarino1 = float.Parse(num1);
            float intarino2 = float.Parse(num2);
            switch (oper)
            {
                case '+':
                    return intarino1 + intarino2;
                case '-':
                    return intarino1 - intarino2;
                case '*':
                    return intarino1 * intarino2;
                case '/':
                    return intarino1 / intarino2;
                default:
                    return 5;
            }
        }




        static void Main()
        {
            string input;
            while (true)
            {
                Console.WriteLine("mathematical expression (type x to exit):");
                input = Console.ReadLine();
                Console.WriteLine($"postfix notation : {InfixPostfix(input)}");
                Console.WriteLine($"result = {EvaluatePostfix(InfixPostfix(input))}");
            }
        }
    }
}