using System;

​

class Mortgage

{

    public double Loan { get; set; }

    public double Rate { get; set; }

    public int Term { get; set; }

​

    private double _payment;

    private double _totalCost;

    private double _totalInterest;

​

    public Mortgage(double loan, double rate, int term)

    {

        Loan = loan;

        Rate = rate;

        Term = term;

        _payment = 0;

        _totalCost = 0;

        _totalInterest = 0;

    }

​

    public double Payment

    {

        get

        {

            if (_payment == 0) _payment = CalcPayment(Loan, Rate, Term);

            return _payment;

        }

    }

​

    public double TotalCost

    {

        get

        {

            if (_totalCost == 0) _totalCost = CalcTotalCost(Payment, Term);

            return _totalCost;

        }

    }

​

    public double TotalInterest

    {

        get

        {

            if (_totalInterest == 0) _totalInterest = CalcTotalInterest(TotalCost, Loan);

            return _totalInterest;

        }

    }

​

    private double CalcPayment(double principal, double annualRate, int months)

    {

        double monthlyRate = (annualRate / 100) / 12;

        return principal * (monthlyRate * Math.Pow(1 + monthlyRate, months)) / (Math.Pow(1 + monthlyRate, months) - 1);

    }

​

    private double CalcTotalCost(double payment, int months)

    {

        return payment * months;

    }

​

    private double CalcTotalInterest(double cost, double principal)

    {

        return cost - principal;

    }

​

    public override string ToString()

    {

        return string.Format("{0,10:C2} {1,6:F2} % {2,8} {3,10:C2} {4,14:C2} {5,12:C2}",

            Loan, Rate, Term, Payment, TotalCost, TotalInterest);

    }

}

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("How many mortgage products would you like to compare? (0 to 10)");

        int numProducts;

        if (int.TryParse(Console.ReadLine(), out numProducts) && numProducts > 0 && numProducts <= 10)

        {

            Mortgage[] mortgages = new Mortgage[numProducts];

            for (int i = 0; i < numProducts; i++)

            {

                Console.WriteLine("\nMortgage Product #{0}", i + 1);

​

                Console.WriteLine("Loan  $ (10000 <= range <= 1000000) : ");

                double loan = PromptForValue(10000, 1000000);

​

                Console.WriteLine("Rate % (0.1 <= range <= 25) : ");

                double rate = PromptForValue(0.1, 25);

​

                Console.WriteLine("Term  mo (60 <= range <= 360) : ");

                int term = (int)PromptForIntValue(60, 360);

​

                mortgages[i] = new Mortgage(loan, rate, term);

            }

​

            Console.WriteLine("\n{0,10} {1,8} {2,8} {3,10} {4,14} {5,12}", "Loan", "Rate", "Months", "Payment", "Total Cost", "Interest");

            Console.WriteLine("========== ======== ======== ========== ============== ============");

            for (int i = 0; i < numProducts; i++)

            {

                Console.WriteLine(mortgages[i]);

            }

        }

        else

        {

            Console.WriteLine("Invalid number of products.");

        }

    }

​

    static double PromptForValue(double min, double max)

    {

        double value;

        do

        {

            if (double.TryParse(Console.ReadLine(), out value) && value >= min && value <= max)

            {

                break;

            }

            Console.WriteLine("Invalid input. Please enter a value between {0} and {1}.", min, max);

        } while (true);

​

        return value;

    }

​

    static int PromptForIntValue(int min, int max)

    {

        int value;

        do

        {

            if (int.TryParse(Console.ReadLine(), out value) && value >= min && value <= max)

            {

                break;

            }

            Console.WriteLine("Invalid input. Please enter a value between {0} and {1}.", min, max);

        } while (true);

​

        return value;

    }

}