C#: الميراث

class Animal
{
    public string Name { get; set; }
    public void Eat()
    {
        Console.WriteLine($"{Name} is eating.");
    }
}

class Dog : Animal
{
    public void Bark()
    {
        Console.WriteLine($"{Name}: Woof!");
    }
}

class Program
{
    static void Main()
    {
        Dog dog = new Dog { Name = "Buddy" };
        dog.Eat();
        dog.Bark();
    }
}

Buddy is eating.
Buddy: Woof!

class Person
{
    public string Name { get; }

    public Person(string name)
    {
        Name = name;
    }

    public virtual void Introduce()
    {
        Console.WriteLine($"I am {Name}.");
    }
}

class Student : Person
{
    public int Grade { get; }

    public Student(string name, int grade) : base(name)
    {
        Grade = grade;
    }

    public override void Introduce()
    {
        base.Introduce();
        Console.WriteLine($"I am in grade {Grade}.");
    }
}

class Program
{
    static void Main()
    {
        Student s = new Student("Alice", 3);
        s.Introduce();
    }
}

I am Alice.
I am in grade 3.

class Shape
{
    public virtual double Area()
    {
        return 0;
    }
}

class Circle : Shape
{
    public double Radius { get; set; }

    public Circle(double radius)
    {
        Radius = radius;
    }

    public override double Area()
    {
        return Math.PI * Radius * Radius;
    }
}

class Rectangle : Shape
{
    public double Width { get; set; }
    public double Height { get; set; }

    public Rectangle(double w, double h)
    {
        Width = w;
        Height = h;
    }

    public override double Area()
    {
        return Width * Height;
    }
}

class Program
{
    static void Main()
    {
        Shape[] shapes = { new Circle(2), new Rectangle(3, 4) };
        foreach (Shape s in shapes)
        {
            Console.WriteLine($"Area: {s.Area():F2}");
        }
    }
}

Area: 12.57
Area: 12.00

class Base
{
    public void Greet()
    {
        Console.WriteLine("Hello from Base");
    }
}

class Derived : Base
{
    public new void Greet()
    {
        Console.WriteLine("Hello from Derived");
    }
}

class Program
{
    static void Main()
    {
        Derived d = new Derived();
        d.Greet();

        Base b = d;
        b.Greet();
    }
}

Hello from Derived
Hello from Base

class Config
{
    public virtual void Load()
    {
        Console.WriteLine("Loading config...");
    }
}

class JsonConfig : Config
{
    public sealed override void Load()
    {
        Console.WriteLine("Loading JSON config...");
    }
}

sealed class FinalClass
{
    public void DoWork() { }
}

class Program
{
    static void Main()
    {
        JsonConfig cfg = new JsonConfig();
        cfg.Load();
    }
}

Loading JSON config...

class Vehicle
{
    public string Type { get; }

    public Vehicle(string type)
    {
        Type = type;
        Console.WriteLine($"Vehicle({type}) constructed");
    }
}

class Car : Vehicle
{
    public string Brand { get; }

    public Car(string brand) : base("Car")
    {
        Brand = brand;
        Console.WriteLine($"Car({brand}) constructed");
    }
}

class Program
{
    static void Main()
    {
        Car car = new Car("Toyota");
    }
}

Vehicle(Car) constructed
Car(Toyota) constructed

class Point
{
    public int X { get; }
    public int Y { get; }

    public Point(int x, int y)
    {
        X = x;
        Y = y;
    }

    public override string ToString()
    {
        return $"({X}, {Y})";
    }

    public override bool Equals(object obj)
    {
        if (obj is Point other)
        {
            return X == other.X && Y == other.Y;
        }
        return false;
    }

    public override int GetHashCode()
    {
        return HashCode.Combine(X, Y);
    }
}

class Program
{
    static void Main()
    {
        Point p1 = new Point(1, 2);
        Point p2 = new Point(1, 2);
        Console.WriteLine(p1.ToString());
        Console.WriteLine(p1.Equals(p2));
        Console.WriteLine(p1.GetType().Name);
    }
}

(1, 2)
True
Point

class Animal { }
class Cat : Animal
{
    public void Meow() { Console.WriteLine("Meow!"); }
}
class Dog : Animal
{
    public void Bark() { Console.WriteLine("Woof!"); }
}

class Program
{
    static void Main()
    {
        Animal a = new Cat();

        if (a is Cat)
        {
            Console.WriteLine("a is a Cat");
        }

        if (a is Dog)
        {
            Console.WriteLine("a is a Dog");
        }
        else
        {
            Console.WriteLine("a is not a Dog");
        }

        Cat c = a as Cat;
        if (c != null)
        {
            c.Meow();
        }

        Dog d = a as Dog;
        Console.WriteLine($"as Dog result is null: {d == null}");
    }
}

a is a Cat
a is not a Dog
Meow!
as Dog result is null: True