Object-Oriented Programming

using System;

// A class is a BLUEPRINT — it describes what every Car will have and do.
// It is not a car you can drive; it's the design on paper.
class Car
{
    // Fields = the data each Car object holds.
    public string Brand;
    public string Model;
    public int Year;

    // A method = something the object can DO.
    public void StartEngine()
    {
        Console.WriteLine($"{Brand} {Model} ({Year}) — engine started! 🚗");
    }
}

class Program
{
    static void Main()
    {
     
...

using System;

// 🎯 YOUR TURN — finish the Rectangle class, then run it.
class Rectangle
{
    // 1) Width is done for you. Add a public int field called Height below it.
    public int Width;
    public int ___;            // 👉 name this field  Height

    // 2) Area() should return Width times Height.
    public int Area()
    {
        return ___;            // 👉 multiply the two fields:  Width * Height
    }
}

class Program
{
    static void Main()
    {
        Rectangle r = new Rectang
...

using System;

class Car
{
    public string Brand;
    public string Model;
    public int Year;

    // A CONSTRUCTOR runs automatically when you write 'new Car(...)'.
    // It has the same name as the class and no return type.
    // 'this.Brand' = THIS object's Brand; 'brand' = the value passed in.
    public Car(string brand, string model, int year)
    {
        this.Brand = brand;    // 'this' makes it clear which is which
        this.Model = model;
        this.Year = year;
    }

    
...

using System;

class Dog
{
    public string Name;
    public string Breed;

    // 🎯 YOUR TURN — finish the constructor and the Main method.

    // 1) Set this object's fields from the values passed in.
    public Dog(string name, string breed)
    {
        this.Name = ___;       // 👉 assign the 'name' parameter to this.Name
        this.Breed = breed;    // (this one is done for you)
    }

    public void Bark()
    {
        Console.WriteLine($"{Name} the {Breed} says Woof! 🐶");
    }
}
...

using System;

class BankAccount
{
    // 'private' means: only code INSIDE this class can touch balance.
    // Outside code cannot read or change it directly — that's the point.
    private double balance;
    public string Owner { get; }   // read-only from outside

    public BankAccount(string owner, double initialBalance)
    {
        Owner = owner;
        balance = initialBalance;
    }

    // Public methods are the ONLY way in — so they can enforce the rules.
    public void Deposit(d
...

using System;

class Student
{
    // Auto-property — the compiler creates the hidden storage for you.
    // This is the everyday default when no validation is needed.
    public string Name { get; set; }

    // Full property — a 'backing field' lets you validate the value.
    private int age;
    public int Age
    {
        get => age;                  // returning the stored value
        set                          // 'value' is whatever was assigned
        {
            if (value < 0 |
...

using System;

class Counter
{
    // STATIC field — ONE copy shared by every Counter object that exists.
    private static int totalCount = 0;

    // INSTANCE field — every object gets its OWN Label.
    public string Label { get; }

    public Counter(string label)
    {
        Label = label;
        totalCount++;                 // bumped each time ANY object is made
    }

    // STATIC method — called on the CLASS, not on an object.
    public static int GetTotalCount() => totalCount;

 
...