using System;

​

public class Mortgage

{

    public double Loan { get; set; }

    public double Rate { get; set; }

    public int Term { get; set; }

    public static double GetDouble(string prompt, double min, double max)

    {

        string input;

        double number;

        do {

            Console.Write(prompt + " ({0} <= range <= {1}) : ", min, max);

            input = Console.ReadLine();

        } while (!double.TryParse(input, out number) || number < min || number > max);

        return number; 

    }

    private int _payment;

    public int Payment 

    {

        // Note that the first time Payment property is "read", 

        // the private _payment field will be set to the return

        // value of the M method, the calculation.

        // Subsequent reads from the property will merely get 

        // the computed and stored value. 

        // 

        // This is called "lazy evaluation", i.e., property 

        // values are only computed if and when they are needed.

        //

        // Use this for computing payment, total cost and interest

        // in HW#4.

        //

        get

        { 

            if (_payment == 0) _payment = M();

            return _payment;

        }

        // No set method! This is a read-only property.

        // The setting of the underlying field is in the get. The M

        // method encapsulates the particular formula.

    }

    public int M()

    {

        // Make sure you are only using constants and properties in this class

        // to calculate the needed value, say the payment or total cost.

        Console.WriteLine("Calculate");

        return 100; //plug in formulas instead of 100

    }

}

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        Mortgage a = new Mortgage();

        a.Loan = Mortgage.GetDouble("Amount", 10000, 1000000);

        a.Rate = Mortgage.GetDouble("Rate", 0.1, 25) / 100;

        Console.WriteLine(a.Payment); // Calculation happens here.

        Console.WriteLine(a.Payment); // All the rest of the references are getting the computed and stored value.

        Console.WriteLine(a.Payment);

        Console.WriteLine(a.Payment);

        Console.WriteLine(a.Payment);

        Console.WriteLine(a.Payment);

        Console.WriteLine(a.Payment);

    }

}