using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        var animal = new Animal(){Name="Bob"};

        //var cat = (Cat)animal;

        var cat = new Cat(){Name = "Bill"};

        Console.WriteLine($"AGE:{cat.Age}");

        cat.Age = 20;

        Console.WriteLine($"AGE:{cat.Age}");

        var animalCasted = (Animal)cat;

        Console.WriteLine($"Name:{animalCasted.Name}");

    }

}

​

public class Animal

{

    public string Name { get; set;}

}

​

public class Cat : Animal

{

    public int Age { get; set;}

}