Polymorphism With Circle Shapes

namespace Polymorphic_Shapes
{
    public class Circle
    {

        private double _radius;

        public Circle(double radius)
        {
            _radius = radius;
        }
        //default constructor
        public Circle()
        {
            _radius = 1;
        }

        public virtual double Radius { get { return _radius; } }
        public virtual double Height { get { return 0; } }

        //the word virtual is added to override or Change circle to sphere)
        public virtual double Area()
        {
            return Math.PI * _radius * _radius;
        }

        public virtual double Perimeter()
        {
            return 2 * Math.PI * _radius;
        }

        public virtual double Volume()
        {
            return 0;
        }
    }
}
//=========================================================
namespace Polymorphic_Shapes
{
    public class Sphere : Circle
    {
        public Sphere(double radius):base(radius)
        {  
        }

        //override methods that are defined as virtual in the parent class
        public override double Area()
        {
            return 4 * Math.PI * Radius * Radius;
        }
        public override double Volume()
        {
            return (4.0 / 3) * Math.PI * Radius * Radius * Radius;
        }
    }
}
//=========================================================
namespace Polymorphic_Shapes
{
    //define a class Cylinder that inherits from Circle
    public class Cylinder : Circle
    {
        private double _height;
        public Cylinder(double radius, double height) : base (radius)
        {
            _height = height;
        }

        public override double Height
        {
            get { return _height; }
        }

        public override double Area()
        {
            return 2 * Math.PI * Radius * Height;
        }

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

}
//=========================================================
namespace Polymorphic_Shapes
{
    public class Cone : Cylinder
    {
        public Cone(double radius, double height): base(radius, height)
        {
            //initialize any fields defined in this class, if any
        }

        public override double Area()
        {
            return Math.PI * Radius * (Radius + Math.Sqrt(Height * Height + Radius * Radius));
        }
        public override double Volume()
        {
            return Math.PI * Radius * Radius * Height / 3;
        }
    }

}
//=========================================================
namespace Polymorphic_Shapes
{
    public partial class Form1 : Form
    {
        //Introduction to polymorphism (polymorphic inheritance)
        //This is the 3rd principle of object-oriented programming
        //the other 2 are: Encapsulation / Data hiding, and Inheritance

        Random rand = new Random();
        public Form1()
        {
            InitializeComponent();
        }

        private void btnCreateRandomCircles_Click(object sender, EventArgs e)
        {
            double radius = rand.Next(10, 20) + rand.NextDouble();
            Circle c = new Circle(radius);
            Display(c);
        }

        private void btnCreateRandomSphere_Click(object sender, EventArgs e)
        {
            double radius = rand.Next(10, 20) + rand.NextDouble();
            Sphere sphere = new Sphere(radius);
            Display(sphere);
        }

        private void Display(Circle cshape)
        {
            double area = cshape.Area();
            double perimeter = cshape.Perimeter();
            double vol = cshape.Volume();
            richTextBox1.AppendText(String.Format("Type: {0} Radius: {1:f} Area : {2:f} Peri: {3:f} Volume: {4:f} \n\n",
                cshape.GetType().Name, cshape.Radius, area, perimeter, vol ));
        }

        private void btnCreateCylinder_Click(object sender, EventArgs e)
        {                                                                                                      
            double radius = rand.Next(10, 20) + rand.NextDouble();
            double h = rand.Next(15, 25) + rand.NextDouble();
            Cylinder cy = new Cylinder(radius, h);
            Display(cy);
        }

        private void btnCreateCone_Click(object sender, EventArgs e)
        {
            double radius = rand.Next(10, 20) + rand.NextDouble();
            double h = rand.Next(15, 25) + rand.NextDouble();
            Cone c = new Cone(radius, h);
            Display(c);
        }
    }
}