Mortgage Calculator Error

Xonel

Hi, I have this error in my code that am having difficulties in rectifying it. Initially, my code looked like this..

private void CalculateTheMortgage()
{
// (Loan Value) * (1 + r/12) ^ p = (12x / r) * ((1 + r/12)^p - 1)
// payment = (((Loan Value) * (1 + r/12) ^ p) * r)/ (12 * ((1 + r/12)^p - 1)));
double loanAmount = (double)txtLoanAmount.CurrentValue; // price of total mortgage before down payment
double taxesPerYear = (double)txtPropertyTax.CurrentValue; // this will divided by 12 and added to the monthly payment
double downPayment = (double)txtDownPayment.CurrentValue; // down payment will be subtracted from the loan
double interestRate = (double)udInterest.Value / 100; // calculate interest from 100%
double termOfLoan = (double)(udTerm.Value * 12); // monthly term
double propertyTax = (double)txtPropertyTax.CurrentValue;
double insurance = (double)txtInsurance.CurrentValue;

       double payment =  (loanAmount - downPayment) \* (Math.Pow((1 + interestRate/12), termOfLoan) \* interestRate)/(12 \* (Math.Pow((1+interestRate/12), termOfLoan) - 1));

       // add on a monthly property tax
       payment = payment + (propertyTax + insurance) / 12;

       txtPayment.CurrentValue = (int)payment;
    }

and i changed it a little to this...

private void CalculateTheMortgage()
{
// (Loan Value) * (1 + r/12) ^ p = (12x / r) * ((1 + r/12)^p - 1)
// payment = (((Loan Value) * (1 + r/12) ^ p) * r)/ (12 * ((1 + r/12)^p - 1)));
double loanAmount = Convert.ToDouble(txtLoanAmount.Text);// price of total mortgage before down payment
double taxesPerYear = Convert.ToDouble(txtPropertyTax.Text); // this will divided by 12 and added to the monthly payment
double downPayment = Convert.ToDouble(txtDownPayment.Text); // down payment will be subtracted from the loan
double interestRate = (double)udInterest.Value / 100; // calculate interest from 100%
double termOfLoan = (double)(udTerm.Value * 12); // monthly term
double propertyTax = Convert.ToDouble(txtPropertyTax.Text);
double insurance = Convert.ToDouble(txtInsurance.Text);

        double payment = (loanAmount - downPayment) \* (Math.Pow((1 + interestRate / 12), termOfLoan) \* interestRate) / (12 \* (Math.Pow((1 + inter

PIEBALDconsult

:doh: textbox.Text ?

Xonel

When i write it like this

txtPayment.Text = (int)payment;

am getting this error

Cannot implicitly convert type 'int' to 'string'

with a blue line under '(int)'

JF2015

txtPayment.Text = payment.ToString();

or:

txtPayment.Text = payment.ToString("0.00 $");

V 0

There are many things wrong here.

Convert.ToDouble

will work and is preferable of

(double)somevalue

but the best method is

double.TryParse or int.TryParse

Secondly you need to use

txtPayment.Text = payment.ToString();

and make sure payment is not null. If you do want an integer, you need to indeed first cast the double to an integer and then that integer to a string (or use round and floor functions) Why do you cast to double in these cases?

double interestRate = (double)udInterest.Value / 100; // calculate interest from 100%
double termOfLoan = (double)(udTerm.Value * 12); // monthly term

What is this code for? Own project, a book, homework?

V.

Xonel

:) Can't believe it was that simple.... Thanks a lot! It worked.. :)

ZurdoDev

Don't convert it to int when trying to put it into a textbox.

There are only 10 types of people in the world, those who understand binary and those who don't.

DaveyM69

Very minor, but...

V. wrote:

make sure payment is not null

payment is a double (not double?) so cannot be null ;)

Dave
Binging is like googling, it just feels dirtier. Please take your VB.NET out of our nice case sensitive forum. Astonish us. Be exceptional. (Pete O'Hanlon)
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)

PIEBALDconsult

V. wrote:

and is preferable

No it isn't.

V. wrote:

the best method is

Not when a cast will do.

V 0

You're absolutely right.

V.

BobJanova

double.Parse is not equivalent to a double cast. One does a string-to-number conversion, the other does a number-to-number conversion. You can use Convert.ToDouble to do either, but I disagree that it's preferable for either scenario: use the mechanism that makes sense in context. A cast translates to a single IL opcode, not a whole method call, after all.