ירושה - שימוש בבנאים (Constructors)

public abstract class Account
{
    private static int nextAccountNumber = 1000;

    private int accountNumber;
    private string owner;
    protected double balance;  // protected כדי שמחלקות נגזרות יוכלו לגשת
    private DateTime createdDate;

    // בנאי סטטי - אתחול מונה חשבונות
    static Account()
    {
        Console.WriteLine("Banking system initialized");
        // ניתן לטעון את המספר האחרון מבסיס נתונים
    }

    // בנאי מוגן למחלקות נגזרות
    protected Account(string owner, double initialBalance)
    {
        if (string.IsNullOrEmpty(owner))
            throw new ArgumentException("Owner name is required");

        if (initialBalance < 0)
            throw new ArgumentException("Initial balance cannot be negative");

        accountNumber = nextAccountNumber++;
        this.owner = owner;
        this.balance = initialBalance;
        this.createdDate = DateTime.Now;

        Console.WriteLine($"Account #{accountNumber} created for {owner}");
    }

    // Getters
    public int GetAccountNumber() => accountNumber;
    public string GetOwner() { return owner; }
    public double GetBalance() { return balance; }
    public DateTime GetCreatedDate() { return createdDate; }

    // Protected setter for balance - למחלקות נגזרות
    protected void SetBalance(double balance) { this.balance = balance; }
}

public class SavingsAccount : Account
{
    private double interestRate;

    // שרשור לבנאי הבסיס
    public SavingsAccount(string owner, double initialBalance, double interestRate)
        : base(owner, initialBalance)
    {
        if (interestRate < 0 || interestRate > 0.1)
            throw new ArgumentException("Invalid interest rate");

        this.interestRate = interestRate;
        Console.WriteLine($"Savings account with {interestRate:P} interest");
    }

    // בנאי נוחות עם ריבית ברירת מחדל
    public SavingsAccount(string owner, double initialBalance)
        : this(owner, initialBalance, 0.02)  // 2% ברירת מחדל
    {
    }

    // Getters and Setters
    public double GetInterestRate() { return interestRate; }
    public void SetInterestRate(double rate)
    {
        if (rate >= 0 && rate <= 0.1)
            this.interestRate = rate;
    }
}

public class CheckingAccount : Account
{
    private double overdraftLimit;

    public CheckingAccount(string owner, double initialBalance, double overdraftLimit)
        : base(owner, initialBalance)
    {
        if (overdraftLimit < 0)
            throw new ArgumentException("Overdraft limit cannot be negative");

        this.overdraftLimit = overdraftLimit;
        Console.WriteLine($"Checking account with ${overdraftLimit} overdraft");
    }

    // בנאי ללא אוברדרפט
    public CheckingAccount(string owner, double initialBalance)
        : this(owner, initialBalance, 0)
    {
    }

    // Getters and Setters
    public double GetOverdraftLimit() { return overdraftLimit; }
    public void SetOverdraftLimit(double limit)
    {
        if (limit >= 0)
            this.overdraftLimit = limit;
    }
}

// שימוש
public class BankingApp
{
    public static void Main()
    {
        var savings = new SavingsAccount("Alice", 1000);
        var checking = new CheckingAccount("Bob", 500, 200);
        var vipSavings = new SavingsAccount("Charlie", 10000, 0.05);

        // שימוש ב-Getters
        Console.WriteLine($"Alice's balance: ${savings.GetBalance()}");
        Console.WriteLine($"Bob's overdraft: ${checking.GetOverdraftLimit()}");
        Console.WriteLine($"Charlie's interest rate: {vipSavings.GetInterestRate():P}");

        /* פלט:
        Banking system initialized
        Account #1000 created for Alice
        Savings account with 2.00% interest
        Account #1001 created for Bob
        Checking account with $200 overdraft
        Account #1002 created for Charlie
        Savings account with 5.00% interest
        Alice's balance: $1000
        Bob's overdraft: $200
        Charlie's interest rate: 5.00%
        */
    }
}