Troubles with my code

[modonnell]

I am currently taking a course that is attempting to teach me coding however I have having a fair amount of trouble with it. I am stuck with one set of code that just doesn't seem to want to work.


The assignment I am trying to complete is:

Write a program to analyze a mortgage. I should enter the load, annual percentage rate of interest, and the duration of the loan in months.

when the button is clicked, the monthly payment and the total amount of interest paid should be displayed. The formula for the monthly payment as given by the book is.

payment = p*r/(1 -(1 +r)^(-n)) Where p is the amount of the loan, r is the monthly interest rate (Annual rate divided by 12) given as a number between 0 (for 0 percent) and 1 (for 100 percent), and n is the duration of the loan in months.

My code is as follows:

Public Class Form1
 
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim rate As Double
        Dim prin As Double
        Dim term As Double
        Dim thePay As Double
        Dim totalInterest As Double
 
        If TextBoxPrin.Text = "" Then MsgBox("Enter Principle")
        If TextBoxRate.Text = "" Then MsgBox("Enter Interest")
        If TextBoxTerm.Text = "" Then MsgBox("Enter Term")
 
        If Not Double.TryParse(TextBoxPrin.Text, prin) Then
            Exit Sub
        End If
 
        If Not Double.TryParse(TextBoxInterest.Text, rate) Then
            Exit Sub
        End If
 
        If Not Double.TryParse(TextBoxTerm.Text, term) Then
            Exit Sub
        End If
 
        If rate >= 1 Then rate = rate / 100
        rate = rate / 12
        thePay = -((prin * rate) / (1 - ((1 + rate) ^ -term)))
        totalInterest = ((term * thePay) - (-prin))
 
        TextBoxPayment.Text = thePay.ToString
 
        TextBoxInterest.Text = totalInterest.ToString
    End Sub
End Class

When I enter the values for the principle ($18,000), rate(5.25%), and term (60 months) and press the button, nothing shows up in the payment textbox nor the interest textbox.

I am stuck, any help would be greatly appreciated

I am also new to the forums so if this is incorrectly posted, I am sorry.

[FunkyDexter]

I am also new to the forums so if this is incorrectly posted, I am sorry

You got it pretty much right. The only thing you could have done better was was to use the highlight or code tags (see the VB and # buttons) to make your code a litle more reasonable. I've added them for you.

I can't see any obvious reason why your code would fail but, if you're not seeing an error message, I would guess that one of your Double.TryParses is failing and an Exit Sub is being called. My suggestion would be to add some message boxes before the Exit Subs.

Other than that, have you worked out how to debug your code and walk through it yet? If so, put a break point at the start of the function then step through the code a line at a time and see what happens.

Welcome to the forum.


edit> Hang on, when you say: "I enter the values for the principle ($18,000), rate(5.25%), and term (60 months)" do you mean you actualy type in the $, % and months characters/words? If so then that's your problem. $60 can't be parsed to a double. 60 can. You should either type only the numbers or you should add code to extract the numbers from the user input

[Sitten Spynne]

Code like this is how you make nothing happen when something goes wrong:

If Not Double.TryParse(TextBoxPrin.Text, prin) Then
    Exit Sub
End If

But the problem is, when you do that, nothing happens when something goes wrong. If there's a problem with your input, you don't get any indicator other than you don't get the results you should expect.

At least when debugging, put some Console.WriteLine() or MessageBox.Show() calls that tell you about what's going on:

If Not Double.TryParse(TextBoxPrin.Text, prin) Then
    MessageBox.Show("Whoa, something's wrong with Prin!")
End If

I'm pretty sure FunkyDexter is right about the problem. Computers are stuffy, and if you ask them to tell you what number "$25,000" is they'll say "$ is not a number". You have to go out of your way to deal with dollar signs and digit separators. It's not very far out of your way, but if you're just getting started you can probably just live with "don't type those things".