// 베이스 클래스
public class Animal
{
    public string Name { get; set; }
    public int Age { get; set; }
}

// 파생클래스
public class Dog : Animal
{
    public void HowOld()
    {
        // 베이스 클래스의 Age 속성 사용
        Console.WriteLine("나이: {0}", this.Age);
    }
}

public class Bird : Animal
{
    public void Fly()
    {
        Console.WriteLine("{0}가 날다", this.Name);
    }
}


public class VirBase
{
    public virtual void Say()
    {
        Console.WriteLine("Hello");
    }
}

public class SpeakerA : VirBase
{
    public override void Say()
    {
        Console.WriteLine("World");
    }
}

public abstract class PureBase
{
    // abstract C#키워드 
    public abstract int GetFirst();
    public abstract int GetNext();
}

public class DerivedA : PureBase
{
    private int no = 1;

    // override C#키워드 
    public override int GetFirst()
    {
        return no;
    }

    public override int GetNext()
    {
        return ++no;
    }
}

public class MyBase
{
    public string Name { get; set; }
    protected int Age { get; set; }
}

public class MyDerived : MyBase
{
    public void Run()
    {
        // 파생클래스이므로 Age 사용 가능
        Console.WriteLine("나이: {0}", this.Age);
    }
}

internal class Program
{
    private static void Main(string[] args)
    {
        var dog = new Dog();
        dog.Name = "멍멍이";
        dog.Age = 10;
        var bird = new Bird();
        bird.Name = "삐약이";

        dog.HowOld();
        bird.Fly();

        Animal[] animals = { dog, bird };
        foreach (var animal in animals)
        {
            Console.WriteLine($"{animal.Name}");
        }

    }
    public void Test(object obj)
    {
        // as 연산자
        MyBase a = obj as MyBase;

        // is 연산자
        bool ok = obj is MyBase; //true

        // Explicit Casting
        MyBase b = (MyBase)obj;
    }

}