перевод инфикса в постфикс и его решение

using System;
using System.Collections.Generic;

namespace постфикс
{
    class Program
    {
        static void Main(string[] args)
        {
             // var inFix = "1*2+3-4/5";

            var inFix = "((1+2)*(5+3))/((7-5)*(8-2))";

           // var inFix = "(a*(b+c)+d)/2";

            var postfix = ToPostfix(inFix);

            Console.WriteLine(postfix);

            var solving = SolvePostfix(postfix);

            Console.WriteLine(solving);
        }


        public static double SolvePostfix(string postFix)
        {
            var stackNumbers = new Stack<double>();

            foreach (var ch in postFix)
                if (Char.IsDigit(ch)) stackNumbers.Push(ch-48);
                else if (IsOperation(ch))
                    stackNumbers.Push(OperationBetweenTwoOperands(stackNumbers.Pop(), stackNumbers.Pop(), ch));

            return stackNumbers.Pop();
        }

        public static string ToPostfix(string inFix)
        {
            var postFix = string.Empty;

            var stackOperations = new Stack<char>();

            foreach (var ch in inFix)
            {
                if (Char.IsLetterOrDigit(ch))
                {
                    postFix += ch;
                }
                else if (IsOperation(ch))
                {
                    if ((stackOperations.Count == 0) || ch == '(' || stackOperations.Peek() == '(')
                    {
                        stackOperations.Push(ch);
                    }
                    else if ((ch != ')') && (GetPriority(ch) > GetPriority(stackOperations.Peek())))
                    {
                        stackOperations.Push(ch);
                    }
                    else if ((ch != ')') && (GetPriority(ch) <= GetPriority(stackOperations.Peek())))
                    {
                        while ((stackOperations.Count != 0) && ((stackOperations.Peek() != '(') || (GetPriority(stackOperations.Peek()) >= GetPriority(ch))))
                            postFix += stackOperations.Pop();
                        stackOperations.Push(ch);
                    }
                    else if (ch == ')')
                    {
                        while (stackOperations.Peek() != '(') postFix += stackOperations.Pop();
                        stackOperations.Pop();
                    }
                }
            }

            while (stackOperations.Count != 0) postFix += stackOperations.Pop();

            return postFix;
        }

        public static double OperationBetweenTwoOperands(double left,double right,char operation)
        {
            if (!IsOperation(operation)) throw new InvalidOperationException("Это не операция");
            switch(operation)
            {
                case '+' : return right + left;
                case '-' : return right - left;
                case '*' : return right * left;
                case '/' : return right / left;
                default : return 0;
            }
        }

        public static bool IsOperation(char x) =>
            (x == '(' || x == '+' || x == '-' || x == '*' || x == '/' || x == ')');
        public static int GetPriority(char operation)
        {
            switch (operation)
            {
                case '(': return 0;
                case '+': return 1;
                case '-': return 1;
                case '*': return 2;
                case '/': return 2;
            }
            return -1;
        }
    }
}