Encapsulated State

Methods can change private state while the class controls what is allowed.

EncapsulatedState.cs

using System;

class Wallet
{
    private int cents;

    public int Cents
    {
        get { return cents; }
    }

    public void Deposit(int amount)
    {
        if (amount > 0)
        {
            cents += amount;
        }
    }

    public bool Spend(int amount)
    {
        if (amount <= cents)
        {
            cents -= amount;
            return true;
        }

        return false;
    }
}

class Program
{
    static void Main()
    {
        int spend = ;
        Wallet wallet = new Wallet();
        wallet.Deposit(50);
        bool paid = wallet.Spend(spend);

        Console.WriteLine($"spend={spend}");
        Console.WriteLine($"paid={paid}");
        Console.WriteLine($"remaining={wallet.Cents}");
    }
}

using System;

class Wallet
{
    private int cents;

    public int Cents
    {
        get { return cents; }
    }

    public void Deposit(int amount)
    {
        if (amount > 0)
        {
            cents += amount;
        }
    }

    public bool Spend(int amount)
    {
        if (amount <= cents)
        {
            cents -= amount;
            return true;
        }

        return false;
    }
}

class Program
{
    static void Main()
    {
        int spend = ;
        Wallet wallet = new Wallet();
        wallet.Deposit(50);
        bool paid = wallet.Spend(spend);

        Console.WriteLine($"spend={spend}");
        Console.WriteLine($"paid={paid}");
        Console.WriteLine($"remaining={wallet.Cents}");
    }
}

using System;

class Wallet
{
    private int cents;

    public int Cents
    {
        get { return cents; }
    }

    public void Deposit(int amount)
    {
        if (amount > 0)
        {
            cents += amount;
        }
    }

    public bool Spend(int amount)
    {
        if (amount <= cents)
        {
            cents -= amount;
            return true;
        }

        return false;
    }
}

class Program
{
    static void Main()
    {
        int spend = ;
        Wallet wallet = new Wallet();
        wallet.Deposit(50);
        bool paid = wallet.Spend(spend);

        Console.WriteLine($"spend={spend}");
        Console.WriteLine($"paid={paid}");
        Console.WriteLine($"remaining={wallet.Cents}");
    }
}

encapsulation Encapsulation keeps state changes inside the object that owns the state.