problems with variables on Visual Basic

Question

I'm trying to calculate tip using radio buttons and use them to select the percentage but the variable "tip" doesn't transfer over to the next sub and lblTip.text keeps coming up as 0

Here's my code:

Public Class Form1
Dim tip As Double
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnExit.Click
    Me.Close()
End Sub


Private Sub btnDisplay_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnDisplay.Click

    Select Case True
        Case rbtnTen.Checked
            tip = 0.1
        Case rbtnFifteen.Checked
            tip = 0.15
        Case rbtnTwenty.Checked
            tip = 0.2
    End Select

End Sub

Private Sub btnCalcTip_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnCalcTip.Click
    lblTip.Text = Val(txtBill.Text) * tip
End Sub
End Class

What do you mean for "the variable "tip" doesn't transfer over to the next sub"? — Angelo Badellino
– Angelo Badellino, Commented Feb 13, 2012 at 15:47
Did you debug to make sure the tip is correctly assigned inside btnDisplay_Click? — Meta-Knight
– Meta-Knight, Commented Feb 13, 2012 at 15:48
Just an fyi, but .1 is a repeating decimal when converted to binary, which could cause you to see some unexpected results here. Since these are monetary calculations, try having your tip variable be a Decimal instead of a Double. — Joel Coehoorn
– Joel Coehoorn, Commented Feb 13, 2012 at 15:55
Two important notes: 1) Select Case True is considered bad programming practise you could use If Then ElseIf End If in this scenario, 2) You should switch Option Strict On - this would alert you to an error in the code you posted — Matt Wilko
– Matt Wilko, Commented Feb 13, 2012 at 16:07
Thanks Matt. I'm kinda knew to VB so any tips would be helpful — Kentaro51
– Kentaro51, Commented Feb 14, 2012 at 14:47

APrough · Accepted Answer · 2012-02-13 21:28:27Z

1

As is, your code works fine, but a couple of things...

Use the If..ElseIf..EndIF that everyone mentions.
Try not to use Val (It works in this situation, but it may not in all)

As for why you are getting only 0, I was able to replicate that behavior using your existing code, by one of the threefollowing...

Don't click btnDisplay first. In this case, you do not assign a value to tip, so it defaults to 0. Multiply 0 by any amount and you get... 0.
Not having a value in TxtBill. Same reason as #1.
Not have a default value for the radio buttons set, and trying to calculate.

Assuming I put a value in txtBill, choose a tip option and pressed btnDisplay, I get a value.

I would put breaks in and trying to track the values in your variables to see what is going on. You could also probably make btnDisplay and btnCalc do all the work at once (verify that a tip amount has been chosen, and do calc and display results). No point in clicking two buttons.

answered Feb 13, 2012 at 21:28

APrough

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1 Comment

Kentaro51 Over a year ago

thanks. i got rid of btnDisplay and it's working now. Thanks again for the help.

MunkiPhD · Accepted Answer · 2012-02-13 17:23:57Z

0

Using Val() is usually not recommended (especially in i18n code). It's a carry over from Visual Basic (pre .Net) and it creates all types of funky data when parsing values. It's recommended to clean the string first then parse it, i.e. stripping dollar signs, then parse the value as a single/double.

For more info on Val() look at the corresponding MSDN page.

answered Feb 13, 2012 at 17:23

MunkiPhD

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Comments

zzzzzzzzzzzzzzzzzzzzzzzzzzzzzz · Accepted Answer · 2012-02-13 19:26:33Z

0

Have you tried:

lblTip.Text = CStr(CDbl(txtBill.Text) * tip)

How about ElseIf statements instead of your case statement:

If rbtnTen.Checked Then
    tip = 0.1
ElseIf rbtnFifteen.Checked Then
    tip = 0.15
ElseIf rbtnTwenty.Checked Then
    tip = 0.2
EndIf

edited Feb 13, 2012 at 19:26

answered Feb 13, 2012 at 15:46

zzzzzzzzzzzzzzzzzzzzzzzzzzzzzz

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3 Comments

Meta-Knight Over a year ago

OP says that his problem is that "lblTip.text keeps coming up as 0". This wouldn't fix the problem.

zzzzzzzzzzzzzzzzzzzzzzzzzzzzzz Over a year ago

It would if there is an issue parsing the integer as a string. lblTip.Text stores a string value not an integer value. The problem also may reside in Val(txtBill.Text)

Meta-Knight Over a year ago

My point is: If CDbl(txtBill.Text) * tip returns 0, then wrapping this code with CStr will still return 0!

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