Example of a BMI thingy.cs

using System;

namespace Data_Projekt_2020_EUX
{
    class Program
    {
        /* public boolean that is accessable from all functions. its good to just throw this outside the scope, 
         * because it will allow all methods in the future to read what your program is at .. at the moment.*/
        public static bool Done = false; 

        static void Main(string[] args)
        {
            /* Where we define the main program loop that will go on until we say we are done. */
            while (Done == false)
            {
                Console.WriteLine("CPR number format xxxxxx-xxxx example (270102-1234)");
                Console.Write("Input CPR number: ");
                string CPR = Console.ReadLine();
                string DateOfBirth = CPR.Substring(0, 6);
                DateTime dateofbirth = DateTime.ParseExact(DateOfBirth, "ddMMyy", null);
                DateTime age = (new DateTime(1, 1, 1) + (DateTime.Now - dateofbirth));
                int personsAge = age.Year - 1;
                bool male = Convert.ToInt32(CPR.Substring(CPR.Length - 1, 1)) % 2 != 0;
                Console.Clear();
                Console.WriteLine("Height in centimeters example (173)");
                Console.Write("Input Height: ");
                double Height = Convert.ToDouble(Console.ReadLine());
                Console.Clear();
                Console.WriteLine("Weight in kilograms example (42)");
                Console.Write("Input Weight: ");
                double Weight = Convert.ToDouble(Console.ReadLine());
                Console.Clear();

                Console.WriteLine("Personal data:");
                Console.WriteLine("Age: " + personsAge.ToString());
                if (male)
                {
                    Console.WriteLine("Gender: Male");
                }
                else
                {
                    Console.WriteLine("Gender: Female");
                }
                Console.WriteLine("Height: " + Height);
                Console.WriteLine("Weight: " + Weight);
                

                // add a menu loop state
                bool menuLoop = true;
                while (menuLoop)
                {
                    Console.WriteLine(string.Empty);
                    Console.WriteLine("Control Menu:");
                    Console.WriteLine("[1] Calculate BMI");
                    Console.WriteLine("[2] Calculate energy needs");
                    Console.WriteLine("[3] Calculate big mac calories and how many km to run to burn them");
                    Console.WriteLine("[4] Enter a different set of personal stats");
                    Console.WriteLine("[5] Exit program");
                    Console.WriteLine("[#] Input Choise: ");

                    int userChoise = Convert.ToInt32(Console.ReadLine());

                    switch (userChoise)
                    {
                        case 1: BMICalc(Height, Weight, male, personsAge); break;
                        case 2: EnergiCalc(Height, Weight, male, personsAge); break;
                        case 3: BigMacCalc(Height, Weight, male, personsAge); break;
                        case 4: menuLoop = false; break; // set the menu loop state to false so we start from scratch
                        case 5:
                            {
                                menuLoop = false;
                                Done = true;
                            } break;
                        default: Console.WriteLine("You're too drunk to calculate shitz."); break;
                    }
                }
            }
        }

        private static void BigMacCalc(double Height, double Weight, bool male, int age)
        {
            Console.Clear();
            Console.WriteLine("Personal data:");
            Console.WriteLine("Age: " + age.ToString());
            if (male)
            {
                Console.WriteLine("Gender: Male");
            }
            else
            {
                Console.WriteLine("Gender: Female");
            }
            Console.WriteLine("Height: " + Height);
            Console.WriteLine("Weight: " + Weight);
            Console.WriteLine(string.Empty);
            Console.Write("How many big mac's would you like to burn?: ");
            double BigMacAmount = Convert.ToDouble(Console.ReadLine());
            int CaloriesPer = 503;
            double TotalCalories = BigMacAmount * CaloriesPer;
            double AmountToRun = TotalCalories / Weight;
            Console.WriteLine(string.Empty);
            Console.WriteLine("You have to run " + AmountToRun + "km");
            ExitOption();
        }

        private static void EnergiCalc(double Height, double Weight, bool male, int age)
        {
            Console.Clear();
            Console.WriteLine("Personal data:");
            Console.WriteLine("Age: " + age.ToString());
            if (male)
            {
                Console.WriteLine("Gender: Male");
            }
            else
            {
                Console.WriteLine("Gender: Female");
            }
            Console.WriteLine("Height: " + Height);
            Console.WriteLine("Weight: " + Weight);
            Console.WriteLine(string.Empty);
            double energy = 0.0;
            if (male)
            {
                energy = ((Weight * 42.0) + (Height * 26.3) - (age * 20.7) - 676.2) / 4.2;
                Console.WriteLine("You need " + energy + " kcal per day");
            }
            else
            {
                energy = ((Weight * 42.0) + (Height * 26.3) - (age * 20.7) + 21) / 4.2;
                Console.WriteLine("You need " + energy + " kcal per day");
            }
            ExitOption();
        }

        private static void BMICalc(double Height, double Weight, bool male, int age)
        {
            Console.Clear();
            Console.WriteLine("Personal data:");
            Console.WriteLine("Age: " + age.ToString());
            if (male)
            {
                Console.WriteLine("Gender: Male");
            }
            else
            {
                Console.WriteLine("Gender: Female");
            }
            Console.WriteLine("Height: " + Height);
            Console.WriteLine("Weight: " + Weight);
            Console.WriteLine(string.Empty);
            double Height2 = Height * Height;
            double BMI = Weight / Height2;
            double BMIResult = BMI * 10000;
            Console.WriteLine("BMI: " + BMIResult);
            ExitOption(); // here it is called as an example
        }

        /* a small helper function, so you dont have to write the same douplicate code in every function ..*/
        private static void ExitOption()
        {
            Console.WriteLine("Wanna exit or try again??");
            string option = Console.ReadLine();
            if(option.ToLower() == "n")
            {
                Environment.Exit(1);
            }
        }
    }
}