VB.NET reading CSV and adding new fields conditionally

Question

When running debugger, i am getting the following error,

A first chance exception of type 'System.IndexOutOfRangeException' occurred in HSL File Config.exe Additional information: Index was outside the bounds of the array. An unhandled exception of type 'System.IndexOutOfRangeException' occurred in HSL File Config.exe Additional information: Index was outside the bounds of the array. The program '[14044] HSL File Config.vshost.exe: Managed (v4.0.30319)' has exited with code 0 (0x0).

i have checked the csv data file im loading is in fact 30 columns long and no blank lines. there are however some blank fields.

    Dim FileName = tbOpen.Text
    Dim fileout = tbSave.Text
    Dim lines = File.ReadAllLines(FileName)
    Dim output As New List(Of String)

    For Each line In lines
        Dim fields = line.Split(","c)
        If fields(0) = "R62167" Then
            ReDim Preserve fields(fields.Length)
            fields(31) = "9991"
        End If
        If fields(0) = "R62193" Then
            ReDim Preserve fields(fields.Length)
            fields(32) = "1999"
        End If
        If fields(2) = "2249" Then
            fields(2) = "0000"
        End If

        output.Add(String.Join(","c, fields))
    Next
    File.WriteAllLines(fileout, output)

Mukul Varshney · Accepted Answer · 2016-09-19 11:31:41Z

1

Use redim

If fields(5) = "4WK" Then
    ReDim Preserve fields(fields.Length)
    fields(6) = "NewDate"
End If

answered Sep 19, 2016 at 11:31

Mukul Varshney

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3 Comments

JustAnAverageSQLuser Over a year ago

Thanks Mukul Varshney, you have saved my bacon! amazing. cant believe it was something so simple :)

JustAnAverageSQLuser Over a year ago

thanks for the info, but getting errors with larger data sets (around 30 columns) A first chance exception of type 'System.ArgumentOutOfRangeException' occurred in mscorlib.dll

Mukul Varshney Over a year ago

Will suggest you to define fields array with an expected maximum columns, outside the for loop. use a variable count to update the fields value. fields(counter) = "NewDate" counter = counter +1, once you add a value, or declare fields as a List. This will be similar to what @FloatingKiwi suggested.

FloatingKiwi · Accepted Answer · 2016-09-19 10:45:41Z

0

Instead of using Fields as an array try it as a list as these are resizable.

Dim fields = line.Split(","c).ToList()

then you can do

If fields(5) = "4WK" Then
    fields.Add("NewDate")
End If

answered Sep 19, 2016 at 10:45

FloatingKiwi

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8 Comments

JustAnAverageSQLuser Over a year ago

Thanks both. this seems to work well with small amounts of data, but once i try it with the real file im trying to manipulate i get A first chance exception of type 'System.ArgumentOutOfRangeException' occurred in mscorlib.dll errors any ideas? code snippit to follow

JustAnAverageSQLuser Over a year ago

Dim FileName = tbOpen.Text Dim fileout = tbSave.Text Dim lines = File.ReadAllLines(FileName) Dim output As New List(Of String) For Each line In lines ' version 1 Dim fields = line.Split(","c) Dim fields = line.Split(","c).ToList() If fields(28) = "ZIPSPEED" Then fields.Add("NewDateD") End If output.Add(String.Join(","c, fields)) Next File.WriteAllLines(fileout, output)

JustAnAverageSQLuser Over a year ago

it seems to fail on any field other than fields(0) if that helps?

FloatingKiwi Over a year ago

I suspect you have a blank line in your file so splitting it yields just a blank string. So test whether your fields has at least 29 fields before processing the fields. Please get acquainted with the debugger as these issues are quicker to fix yourself than posting on SO and waiting for a reply

FloatingKiwi Over a year ago

Your asking for an element that doesn't exist. When you split the string you didn't end up with your expected number of strings. Use a debugger and look at the values, it'll be blatantly obvious what is wrong.

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