using System;

// BankAccount class

public class BankAccount

{

    // 1. [Code] Create properties

    //    (a) AccountID: protected string

    //    (b) OwnerName: public string

    //    (c) Balance: public double

    //    (d) OpeningYear: private int

    protected string AccountID;

    public string OwnerName;

    public double Balance;

    private int OpeningYear;

    // Default constructor

    public BankAccount() { }

    // 2. [Code] Create the second constructor with 4 parameters to set up those 4 properties

    public BankAccount(string a, string o, double b, int op) {

        AccountID = a;

        OwnerName = o;

        Balance = b;

        OpeningYear = op;

    }

    // 3. [Code] Create function: PrintOwnerName

    //    input: no

    //    ouput: no

    //    behaviors: print out owner's name

    public void PrintOwnerName() {

        Console.WriteLine("Owner's Name: {0}", OwnerName);  

    }

    // 4. [Code] Create function: ShowBalance

    //    input: no

    //    ouput: no

    //    behaviors: print out balance

    //    Note: add keyword "virtual" to allow override later

    public virtual void ShowBalance() {

        Console.WriteLine("Balance: ${0}", Balance);    

    }

}

​

// CheckingAccount class

public class CheckingAccount : BankAccount

{

    // Properties

    public int WithdrawLimit {get; set;}

    // Default construtor

    public CheckingAccount() { }

    // 5. [Code] Create the second constructor with 5 parameters

    //    (a) use keyword "base" to call parent's constructor (hint: need to pass 4 parameters)

    //    (b) set up WithdrawLimit

    public CheckingAccount(string a, string o, double b, int op, int w): base(a, o, b, op) {

        WithdrawLimit = w;

    }

    // 6. [Code] Create function: PrintOwnerName

    //    input: no

    //    ouput: no

    //    behaviors: Console.WriteLine("CheckingAccount OwnerName: " + OwnerName);

    //    Use Method Hiding (Hint: use new keyword)

    public new void PrintOwnerName() {

        Console.WriteLine("CheckingAccount Owner Name: " + OwnerName);

    }

    // 7. [Code] Create function: ShowBalance

    //    input: no

    //    ouput: no

    //    behaviors: Console.WriteLine("CheckingAccount Balance: " + Balance);

    //    Use Method Overriding (Hint: override keyword)

    public override void ShowBalance() {

        Console.WriteLine("CheckingAccount Balance: " + Balance);

    }

    public void Function()

    {   

        // 8. Question

        //    Can you print out AccountID? Why or why not?

        //    Console.WriteLine(AccountID);

        //    [Yes, because it is a protected variable it still can be called in referenced classes]

        //    Can you print out OpeningYear? Why or why not?

        //    Console.WriteLine(OpeningYear);

        //    [No, because it is a private variable it cannot be called anywhere except the base class]

    }

}

​

public class Program

{

    public static void Main()

    {

        // 9. Question

        //    Unmark the following code once you finish both BankAccount and CheckingAccount classes

        //    Answer the following two questions

        CheckingAccount ca = new CheckingAccount( "A12345", "Mary", 5000, 12, 6);

        ca.PrintOwnerName();

        // What is this technique? (a) method hiding, (b) method overriding

        // [A] This is method hiding. ca.PrintOwnerName() calls the "new" method on the derived class

        BankAccount ba = new CheckingAccount("B6789", "John", 3000, 22, 6); 

        // This called "polymorphism", i.e. an instance of a derived class can be stored and used as an instance of the base class.

        // When the virtual method of the object is called, the virtual method on the derived class is called even though the variable is of the base type.

        ba.PrintOwnerName(); // This calls the method of the base

        ba.ShowBalance(); // This calls the virtual method on the derived class

        // What is this technique? (a) method hiding, (b) method overriding

        // [B]

    }

}