Square.cs
Code:
using System;

namespace DemoSquares
{
    public class Square
    {
        private double sideLength;
        private double area;

        public double SideLength {
            get { return this.sideLength; }
        }

        public double Area { 
            get { return this.area; }
        }

        public Square(double squareSideLength)
        {
            this.sideLength = squareSideLength;
            this.area = ComputeArea();
        }

        private double ComputeArea()
        {
            return Math.Pow(this.sideLength, 2);
        }
    }
}

DemoSquares.cs
Code:
using System;

namespace DemoSquares
{
    public class DemoSquares
    {
        public static void Main(string[] args)
        {
            Console.Title = "Demo Squares";
            Console.WriteLine("Area and Side Length of Squares:\n\n");
            Console.WriteLine("{0}\t{1}\t{2}", "#", "Side Length", "Area");
            
            Square[] squares = new Square[11];

            for (int i = 1; i < 10; i++)
            {
                squares[i] = new Square(i);

                Square currentSquare = squares[i];

                Console.WriteLine("{0}\t{1,11}\t{2,4}",
                    i, currentSquare.SideLength, currentSquare.Area);
            }

            Console.Read();
        }
    }
}