C# Exercise: 126 Function calculator, params and return value of Main

// Import the System namespace to use basic classes like Console
using System;

class Program
{
    // Main method to drive the program
    public static int Main(string[] args)
    {
        // Check if the correct number of arguments (3) are passed
        if (args.Length != 3)
        {
            // Return error code 1 if the number of parameters is incorrect
            Console.WriteLine("Error: Please provide two numbers and an operator.");
            return 1;
        }

        // Try to parse the first number from the command line arguments
        double num1;
        if (!double.TryParse(args[0], out num1))
        {
            // Return error code 3 if the first parameter is not a valid number
            Console.WriteLine("Error: The first parameter is not a valid number.");
            return 3;
        }

        // Try to parse the second number from the command line arguments
        double num2;
        if (!double.TryParse(args[2], out num2))
        {
            // Return error code 3 if the third parameter is not a valid number
            Console.WriteLine("Error: The third parameter is not a valid number.");
            return 3;
        }

        // Get the operator from the second parameter
        string operatorSign = args[1];

        // Perform the calculation based on the operator
        double result = 0;
        bool validOperation = true;

        // Switch statement to handle different operations
        switch (operatorSign)
        {
            case "+":
                result = num1 + num2; // Perform addition
                break;
            case "-":
                result = num1 - num2; // Perform subtraction
                break;
            case "*":
            case "x": // Allow 'x' as multiplication sign
                result = num1 * num2; // Perform multiplication
                break;
            case "/":
                if (num2 == 0)
                {
                    // Handle division by zero
                    Console.WriteLine("Error: Cannot divide by zero.");
                    validOperation = false;
                }
                else
                {
                    result = num1 / num2; // Perform division
                }
                break;
            default:
                // Return error code 2 if the operator is invalid
                Console.WriteLine("Error: Invalid operator. Use +, -, *, x, or /.");
                validOperation = false;
                break;
        }

        // Output the result if the operation is valid
        if (validOperation)
        {
            Console.WriteLine($"Result: {result}");
            return 0; // Return 0 to indicate successful operation
        }

        // Return an error code if the operation was not valid
        return 2; // Return error code 2 if the operator is invalid
    }
}