Encapsulation in c#

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace Encapsulation

{

    class Program

    {

        class Rectangle

        {

            //member variables

            public double length;

            public double width;

            public double GetArea()

            {

                return length * width;

            }

            public void Display()

            {

                Console.WriteLine("Length: {0}", length);

                Console.WriteLine("Width: {0}", width);

                Console.WriteLine("Area: {0}", GetArea());

            }

        }//end class Rectangle

        class Rectangle1

        {

            //member variables

            private double length;

            private double width;

            public void Acceptdetails()

            {

                Console.WriteLine("Enter Length in inches: ");

                length = Convert.ToDouble(Console.ReadLine());

                Console.WriteLine("Enter Width in inches: ");

                width = Convert.ToDouble(Console.ReadLine());

            }

            public double GetArea()

            {

                return length * width;

            }

            public void Display()

            {

                Console.WriteLine("Length: {0}", length);

                Console.WriteLine("Width: {0}", width);

                Console.WriteLine("Area: {0}", GetArea());

            }

        }//end class Rectangle1

        class Rectangle2

        {

            //member variables

            internal double length;

            internal double width;

            double GetArea()

            {

                return length * width;

            }

            public void Display()

            {

                Console.WriteLine("Length: {0}", length);

                Console.WriteLine("Width: {0}", width);

                Console.WriteLine("Area: {0}", GetArea());

            }

        }//end class Rectangle2

        static void Main(string[] args)

        {

            Console.WriteLine("Enter 1 for Public Access Specifier");

            Console.WriteLine("Enter 2 for Private Access Specifier");

            Console.WriteLine("Enter 3 for Internal Access Specifier ");

            Console.WriteLine("Enter 4 for Exit");

            Console.WriteLine("Enter your Option");

            int op = Convert.ToInt16(Console.ReadLine());

            Console.Clear();

            switch (op)

            {

                case 1:

                    {

                        Rectangle r = new Rectangle();

                        r.length = 4.5;

                        r.width = 3.5;

                        r.Display();

                        Console.ReadKey();

                        break;

                    }

                case 2:

                    {

                        Rectangle1 r = new Rectangle1();

                        r.Acceptdetails();

                        r.Display();

                        Console.ReadKey();

                        break;

                    }

                case 3:

                    {

                        Rectangle r = new Rectangle();

                        r.length = 4.5;

                        r.width = 3.5;

                        r.Display();

                        Console.ReadKey();

                        break;

                    }

                case 4:

                    {

                        System.Environment.Exit(1);

                        break;

                    }

            }

        }

    }

}