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C# C# Basics (Retired) Perfect Wrap Up

Shadab Khan
Shadab Khan
5,470 Points
Posted by Shadab Khan
Shadab Khan
5,470 Points

Refactoring the Console Calculator

Hi Guys,

I have written a console calculator program that takes two numbers and an operator as an input from the end user and displays the operation result. The program works well; however, I interested to see how can we refactor it any further ? Below is my version of the code. Look forward to hear from you guys.

using System;

namespace ConsoleCalculator
{
    class Program
    {
        static void Main(string[] args)
        {
            //Prompt user to enter first number, operator, and second number until "quit" is entered.
            while (true)
            {
                double firstNumber = 0.0;
                double secondNumber = 0.0;
                double result = 0.0;

                string firstEntry, secondEntry;
                char operation = '\0';

                Console.Write("Enter the first number : ");
                firstEntry = Console.ReadLine();

                if (firstEntry.ToLower() == "quit")
                {
                    break;
                }

                Console.Write("Enter the second number : ");
                secondEntry = Console.ReadLine();

                if(secondEntry.ToLower() == "quit")
                {
                    break;
                }

                try
                {
                    firstNumber = double.Parse(firstEntry);
                    secondNumber = double.Parse(secondEntry);
                }
                catch (Exception)
                {
                    Console.WriteLine("Please enter a valid number for operation.");
                    continue;
                }

                Console.Write("Enter the operator : ");
                operation = char.Parse(Console.ReadLine());

                //Begin operations.

                if (operation == '+')
                {
                    result = firstNumber + secondNumber;
                }
                else if(operation == '-')
                {
                    result = firstNumber - secondNumber;
                }
                else if (operation == '/')
                {
                    result = firstNumber / secondNumber;
                }
                else
                {
                    result = firstNumber * secondNumber;
                }

                Console.WriteLine("The result of operation " + operation + " is : " + result);
            }

            Console.WriteLine("Goodbye!");
        }
    }
}

1 Answer

Allan Clark
Allan Clark
10,810 Points
Allan Clark
Allan Clark
10,810 Points

The main thing I can see that would help with readability is if you refactored out the calculator logic into its own class. I would send in the raw user input into the constructor and let the Calculator class worry about the data validation. That will keep a lot of the try/catch-ing out of the main method. Generally you want to have the main method be as minimal as possible.

Also as a note, once you get the hang of Parse methods and Try/catch-ing those, you can move to the TryParse methods. They essentially encapsulate that whole process and rather than dealing with exceptions you can do a null check or just use the bool returned. The try catch block would turn into this. 

double firstNumber;
if (!double.TryParse("", out firstNumber))
{
            //display error
};

p.s. if you have never seen the 'out' keyword it basically means if the parse is successful it will store it in the variable you pass it.