using System;

public class Program

{

    public static void Main()

    {

            //Declare

            int sumOfSquares = 0, count = 0, start = 1;

            string inputString;

            bool isValid = false;

            char doAgain;

​

            //Prompt - DO NOT assume valid input

            Console.WriteLine(" Looping Demo: Event & Counter Controlled\n");

​

            do

            {

                Console.Write(" Enter the number of loops to perform (2 - 10): ");

                inputString = Console.ReadLine();

​

                // 1. Validation Loop

                while (!isValid)

                {

                    // 2. Validate input is a number

                    if (int.TryParse(inputString, out count))

                    {

                        // 3. Check range of 2 - 10

                        if (count >= 2 && count <= 10)

                        {

                            isValid = true;

                        }//end if

                        else

                        {

                            Console.WriteLine("ERROR: Not in range of 2-10 ... Please try again");

                        }//end else

                    }//end if

                    else

                    {

                        Console.WriteLine("ERROR: Not a number ... Please try again");

                    }//end else

​

                    // 4. Reprompt because of invalid input

                    if (!isValid)

                    {

                        Console.Write(" Enter the number of loops to perform (2 - 10): ");

                        inputString = Console.ReadLine();

                    }//end if

                }//end while

​

                // 5. Loop to Process

                while (start <= count)

                {

                    sumOfSquares += start * start;

                    start++;

                }//end while

​

                // 6. Display

                Console.WriteLine("The sum of squares to {0} = {1}", count, sumOfSquares);

​

                // 7. Prompt to do again

                Console.Write("Do another (Y/N): ");

                doAgain = char.ToUpper(char.Parse(Console.ReadLine()));

​

                // 8. Reset variables

                isValid = false;

                start = 1;

                sumOfSquares = 0;

            } while (doAgain == 'Y');

​

            Console.WriteLine("\nThank you ... goodbye");

​

            // keep the console window open

            Console.ReadLine();

    }

}