problem with calling functions in visual basic

Question

I've been learning visual basic lately and decided to do a some code using functions,file reading and writelines. the way I'm trying to make it work, the code should be getting information from files I've written and should produce a file after the program itself runs, as well as a messagebox popping up to say that the program is finished. However, I currently can't even get the messagebox to pop up. I'm not sure what I've done wrong, and although I know this specific project is an odd one I've included the code for it below in the hopes someone can help me with it as I can't find any examples that are exactly similar to what I'm attempting. Anyways, any help would be appreciated, thank you!

Imports System.IO
Class Form1
    Private Sub Button1_Click(sender As Object, e As EventArgs)
        Dim fs As New System.IO.FileStream("a9output.txt", IO.FileMode.Create, IO.FileAccess.Write)
        Dim w As New StreamWriter(fs)
        Dim sr As IO.StreamReader = IO.File.OpenText("a8.txt")
        While sr.Peek <> -1
            Dim Strinput As String
            Strinput = sr.ReadLine
            Dim input = Strinput.Split(",")
            Dim age As Double = Val(input(3))
            Dim SD = CalcSD(age)
            Dim Tax = CalcTaxable(SD, age, Strinput)
            w.WriteLine("Name: " & input(0))
            w.WriteLine("Taxable Income:" & Tax)
            w.WriteLine("Age:" & input(3))
            w.WriteLine("Program Completed")
            MsgBox("Program Completed!")
        End While

        sr.Close()
        w.Close()
    End Sub
    Function CalcSD(ByVal age As Integer) As Double
        Dim SD As Double
        If age >= 65 Then
            SD = 17500
        Else
            SD = 12500
        End If
        Return SD
    End Function
    Function CalcTaxable(ByVal SD As Double, age As Double, strinput As String) As Double
        Dim sr As IO.StreamReader = IO.File.OpenText("a8.txt")

        Dim sum As Double
        strinput = sr.ReadLine
        Dim Input() = strinput.Split(",")
        Dim name As Double = Val(Input(0))
        Dim income As Double = Val(Input(1))
        Dim contribution As Double = Val(Input(2))
        sum = income - contribution - SD

        Return sum
    End Function
End Class

go through your program with the debugger and see what path it's taking. It could be that the file does not exist in the directory where your program expects it, since you did not use a fully qualified path to the file. — JoelFan
– JoelFan, Commented Nov 18, 2020 at 21:05

Jimi · Accepted Answer · 2020-11-19 14:39:11Z

The problem is CalcTaxable() tries to re-open the same file while the button click handler is still using it. Better to worry about all the file/io in one place, and send the values you read to the methods. Also always use Decimal instead of Double when working with money.

Private Sub Button1_Click(sender As Object, e As EventArgs)       
    Using fs As New FileStream("a9output.txt", IO.FileMode.Create, IO.FileAccess.Write), _
          w As New StreamWriter(fs)

        For Each line As String In File.ReadLines("a8.txt")
            'String.Split() is not your friend. A real csv parser would be much better.
            Dim input() As String = line.Split(","c)
            Dim age As Integer = CInt(input(3))
            Dim income As Decimal = CDec(input(1))
            Dim contribution As Decimal = CDec(input(2))
            Dim Tax As Decimal = CalcTaxable(age, income, contribution)

            w.WriteLine($"Name: {input(0)}{vbCrLf}Taxable Income:{Tax}{vbCrLf}Age:{age}")       
        Next
        w.WriteLine("Program Completed")
        MsgBox("Program Completed")
    End Using
End Sub

Function CalcSD(ByVal age As Integer) As Decimal
    If age >= 65 Then Return 17500.0D
    Return 12500.0D
End Function

Function CalcTaxable(age As Integer, income As Decimal, contribution As Decimal) As Decimal
    Return income - contribution - CalcSD(age)
End Function

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