Need help with mortgage calculator

Umar Anjum

Sorry if this has been posted before but I searched the forum and couldn't find a solution. Basically, I need to create a mortgage calculator in C# that allows the user to input the mortgage amount, the interest rate and the duration of the mortgage, the program has to contain a button which, when pressed, calculates the interest the user has to pay, calculates the total amount the user has to pay and the monthly repayments. Below is a copy of the code I've written so far, I was told to use an integer instead of a float/double by my teacher, who said its more efficient. However, there's an error, as when i run the program and type in all of the text boxes and click on the button the outputs are messed up. If someone could take a look at the code and see what I've done wrong and correct it for me I would really appreciate it. Thanks

public int Amount;

public int InterestRate;

public int LoanDuration;

public int InterestToBePaid;

public int TotalAmountToBePaid;

public int MonthlyRepayments;

public frmMortgageCalculator()

{

InitializeComponent();

}

private void tabpSimpleInterest_Click(object sender, EventArgs e)

{

}

private void btnCalculate_Click(object sender, EventArgs e)

{

try

{

Amount = int.Parse(txtAmount.Text);

InterestRate = int.Parse(txtInterestRate.Text);

LoanDuration = int.Parse(txtDuration.Text);

//Calculates the interest

InterestToBePaid = InterestRate / 100 * Amount;

lblInterestToBePaid.Text = "The Total Interest You Have To Pay Is:" + InterestToBePaid;

// Calculates the total amount

TotalAmountToBePaid = Amount + InterestRate;

lblTotalAmountToBePaid.Text = "The Total Amount You Have To Pay Is:" + TotalAmountToBePaid;

//Calculates the monthly repayments

MonthlyRepayments = Amount + InterestRate / LoanDuration;

lblMonthlyRepayments.Text = "Your Monthly Repayments Are:" + MonthlyRepayments;

}

catch(Exception exc)

{

MessageBox.Show(exc.Message);

}

10 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes12y ago
Accepted answer
Well, I'm pleased to see that you're now using the float type rather than int which makes life easier.

However, as far as the accuracy of the results is concerned, all I can say is that your loan company is going to have a lot of satisfied customers as you're only charging them one month's interest regardless of the term of the loan :)

If level monthly payments of interest and capital are to be made, you really need to use the formula to work out what the amount of the repayment should be. I'd ask your teacher about this formula or check with the other guys in your class to see what they've done.
0
Umar Anjum12y ago
Awesome, I'll buy that then and start learning Java :) Thank you for all of your help. I'll stop taking up your time now and let you get back to your life lol. Have a good day :)
0
Vulpes12y ago
As far as learning Java is concerned, I'd recommend this one given that you already have some programming knowledge:

http://www.amazon.co.uk/Java-The-Complete-Reference-Edition/dp/0071606300
0
Umar Anjum12y ago
Ah, I'll start learning Java then, can you recommend me any good books for beginners to learn Java? And yeah, I heard on xda (forum) that C# does actually perform better than Java, and some developers even tried to port Android to C#, don't know where that project is going but if they succeed then who knows what might happen lol
0
Vulpes12y ago
I'd say that Java is perhaps the easiest of the three to learn, closely followed by C# and then C++ which is by far the hardest.

So, if you're wanting to get into Android programming, then Java is probably your best option as it's the native language for that particular platform.

However, you can use C# for Android and even iOS programming. Check out this link:

http://xamarin.com/android

Personally, I'd choose C# over Java every day of the week, but that's just me :)

0
Umar Anjum12y ago
Lol is it? Thanks, and one question, because i don't actually know any programming language off by heart, and i want to learn, which language would be the best to start with? Because my teacher recommended learning Java first. And to be honest, I really do want to learn Java because I have an Android phone and I'm very much in to Rooting, downloading custom ROMs etc, and I would love to be able to make my own mods and ROMs for Android, but if you had to choose from Java, C++ and C#, which would you say is the easiest to learn, and which language do you recommend me to start learning?
0
Vulpes12y ago
Not at all, Umar.

Glad to see that you've a good sense of humor - it's a valuable adjunct to being a programmer!

0
Umar Anjum12y ago
Yeah, float was more suited for this program than int. And lol, I guess I'll consult my teacher and I'll ask her if it's ok. And the thing about asking my class mates is, they actually don't know how to program, I'm the only one in the class who knows a bit about basic programming, so they actually took my work lol, fun times, but thanks for your help, I appreciate it :)
0
Umar Anjum12y ago
Ah right, and no I haven't been taught that formula, but i did manage to get it working, don't know if the results are 100% accurate but heres the code:
try
{
Amount = float.Parse(txtAmount.Text);
InterestRate = float.Parse(txtInterestRate.Text);
LoanDuration = float.Parse(txtDuration.Text);
//Calculates the Interest
InterestToBePaid = InterestRate / 100;
InterestToBePaid = InterestRate * Amount / 12;
lblInterestToBePaid.Text = "The Total Interest You Have To Pay Is: " + InterestToBePaid;

// Calculates the total amount
TotalAmountToBePaid = Amount + InterestToBePaid;
lblTotalAmountToBePaid.Text = "The Total Amount You Have To Pay Is: " + TotalAmountToBePaid;

//Calculates the monthly repayments
MonthlyRepayments = Amount + InterestToBePaid;
MonthlyRepayments = MonthlyRepayments / LoanDuration;
lblMonthlyRepayments.Text = "Your Monthly Repayments Are: " + MonthlyRepayments;

}

catch(Exception exc)
{
MessageBox.Show(exc.Message);
}

}
0
Vulpes12y ago
Well, it's only more efficient to use the int data type if the quantities you're representing are always whole numbers.

Apart from the loan duration (usually expressed in years), all the other quantities may not be whole numbers and the interest rate probably won't be - it could be 5.25% for example.

So, it's difficult to give a sensible answer to this question in view of what your teacher has said.

However, if we ignore this and stick to ints for everything, your first problem is in this line:

InterestToBePaid = InterestRate / 100 * Amount;

In C#, whenever you divide one int by another, you get an int result. This means that (assuming the interest rate will always be less than 100%), the expression: InterestRate / 100 will always give zero.

To avoid this, at least one of the operands has to be a double (or float), so that floating point arithmetic will be used. You then have to convert the final result back to an int. This can be done as follows:

InterestToBePaid = (int)(InterestRate / 100.0 * Amount);

Notice that this will only be the interest for the first year of the mortgage. In a normal mortgage, capital will also be repaid each year and so the interest for the next year will be lower.

There is a formula for calculating the level monthly repayment (capital + interest) of a mortgage and I was wondering whether you've been taught this formula?

If you have, then this formula should first be used to calculate the monthly repayment and hence the total repayments to be made.

The interest payable will then be the difference between the total repayments and the amount of the loan.

0