using System;

    // Read the instructions carefully and implement.

    //

    // 1.) Use inheritance to show that AndroidPhone is a type of SmartPhone.

    //     - Bonus Points: Modify SmartPhone such that we cannot directly create an instance of SmartPhone. We can only create instances of SmartPhone's children. Removing method bodies is allowed. This is optional.

    //

    // 2.) Initialize the existing variable, _phoneType, inside AndroidPhone's constructor.

    //     - Hint: Check the access modifier(s).

    //     - Bonus Points: Do not use the public keyword for this step. This is optional.

    //

    // 3.) Use polymorphism to make AndroidPhone override SmartPhone's SendSms method such that the owner's user name and birthdate are included.

    //     - Hint: A keyword is missing.

    //     - Bonus Points: Include the owner's age. This is optional.

    //

    // 4.) Write another class named IosPhone. Like AndroidPhone, initialize _phoneType and override SendSms.

    //

    // 5.) In class Program, write a method with (a) for loop(s) to create exactly 10 instances of AndroidPhone and exactly 10 instances of IosPhone. Each AndroidPhone and IosPhone must have a unique OwnerUserName and OwnerBirthdate. The method returns 1 list of exactly 20 items of a combination of IosPhone and AndroidPhone.

    //     - Bonus Points: Instead of making OwnerUserName and OwnerBirthday sequential, make them random. This is optional.

    //     - Bonus Points: Do this with only 1 for loop. This is optional.

    //

    // 6.) In the Main method, call the method created in the previous step and assign the return value to a variable.

    //

    // 7.) Get the item corresponding to the 11th youngest owner, and then call SendSms for that item. Do NOT remove this item from the list.

    //     - Bonus Points: Do this using only 1 line of code. This is optional.

    //

    // 8.) Use (a) Lambda expression(s) to sort the items according to the owners' names, but in descending order.

    //

    // 9.) Use a foreach loop to call SendSms for all 20 items.

    //

    // 10.) Remove all even-positioned items (i.e. 2nd, 4th, 6th, 8th, 10th, 12th, 14th, 16th, 18th, and 20th items) from the list. Then, use a foreach loop to call SendSms for all remaining items.

    //      - Hint: Remember that the position may not necessarily be the same as the index.

    //      - Hint: There should be exactly 10 items remaining after this.

    //      - Bonus Points: Use a loop to remove all even-positioned items. This is optional.

    //

    // 11.) Make SmartPhone implement IDisposable. The Dispose method should write something on the console, and then clear the Id, OwnerUserName, and OwnerBirthdate fields.

​

    public class Program

    {

        public static void Main(string[] args)

        {

            Console.WriteLine("Good morning.");

​

            Console.WriteLine();

​

            Console.WriteLine("The objects are initialized after this line.");

​

            // Write code here to call the new method. (See item 6.)

​

            Console.WriteLine();

​

            Console.WriteLine("The SMS message from the 11th youngest owner is below.");

​

            // Write code here to call SendSms. (See item 7.)

​

            Console.WriteLine();

​

            Console.WriteLine("The SMS messages from all 20 items are below.");

​

            // Write code here to call SendSms. (See items 8 and 9.)

​

            Console.WriteLine();

​

            Console.WriteLine("The SMS messages from the remaining 10 items are below.");

​

            // Write code here to call SendSms. (See item 10.)

​

            Console.WriteLine();

​

            Console.WriteLine("The objects are disposed after this line.");

​

            // Write code here to call Dispose. (See item 11.)

​

            Console.WriteLine();

​

            Console.WriteLine("Thank you.");

        }

​

        // Write a new method here. (See item 5.)

    }

​

    // Modify the following class as needed. (See items 1 to 3.)

    public class SmartPhone

    {

        private string _phoneType;

​

        public SmartPhone()

        {

            _phoneType = "Smart Phone";

            Id = Guid.NewGuid();

        }

​

        public Guid Id { get; private set; }

​

        public string OwnerUserName { get; set; }

​

        public DateTime OwnerBirthdate { get; set; }

​

        public void SendSms(string message)

        {

            Console.WriteLine(message);

            Console.WriteLine("Sent from my {0}.", _phoneType);

        }

    }

​

    // Modify the following class as needed. (See items 1 to 3.)

    public class AndroidPhone

    {

        public AndroidPhone()

        {

        }

    }

​

    // Write a new class here. (See item 4.)