I was following some code presented by another developer and for some reason the program is not reading the txt file that I created with the csv data.

What am I doing wrong?

Option Explicit On
Option Strict On
Imports System
Imports System.IO
Public Class ConverterUpdated
    Dim UnitConvVal As Double ' Global Variable for Unit Value.
    Public Sub DataLoad(ByVal Switch As String)
        Dim tfLines() As String = File.ReadAllLines("C:\data.txt") ' File to load.
        For Each line As String In tfLines ' Load and read all lines in file.
            Dim field As String() = line.Split(","c) ' Split using ,.

            Select Case Switch
                Case "LoadCategory"
                    If field(0) = "Category" Then
                        cboCategory.Items.Add(field(1))
                        cboCategory.SelectedIndex = 0 ' Auto Select first Category.
                    End If

                Case "LoadUnits"
                    If field(0) = CStr(cboCategory.SelectedItem) Then
                        cboConvertTo.Items.Add(field(1))
                        cboConvertTo.SelectedIndex = 0 ' Auto Select first Unit.
                    End If

                Case "SelectUnit"
                    If field(1) = CStr(cboConvertTo.SelectedItem) Then
                        UnitConvVal = CDbl(field(2)) ' Load Unit's Conversion value, store in UnitConvVal as Double.
                    End If
            End Select
        Next
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs)
        DataLoad("LoadCategory") ' Switch to DataLoad to load Categories on form load.
    End Sub

    Private Sub cboCategory_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)
        cboConvertTo.Items.Clear() ' Clear cboConvertTo Combobox when re-loading units after selection change.
        DataLoad("LoadUnits")
    End Sub

    Private Sub cboConvertTo_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)
        DataLoad("SelectUnit")
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)
        If txtInputVal.Text = Nothing Then
            MessageBox.Show("Please Enter A Value to Convert") ' Display message if no value is entered.
        Else
            txtResult.Text = CStr(CDbl(txtInputVal.Text) * UnitConvVal) ' If Value has been entered, compute conversion for unit.
        End If
    End Sub
End Class

This is the information inside C:\data.txt

Category,Weight
Category,Distance
Weight,LB to KG,0.45359237
Weight,KG to LB,2.20462262
Distance,Mile to KM,1.609344
Distance,KM to Mile,0.621371192

OK. I went back through and found a few errors in my original VB code. Here is what I have updated and what the new error is.

Option Explicit On
Option Strict On
Imports System
Imports System.IO
Public Class ConverterUpdated
    Dim UnitConvVal As Double ' Global Variable for Unit Value.

    Public Sub DataLoad(ByVal Switch As String)
        Dim tfLines() As String = File.ReadAllLines("C:\data.txt") ' File to load.

        For Each line As String In tfLines ' Load and read all lines in file.
            Dim field As String() = line.Split(","c) ' Split using ,.
            Select Case Switch
                Case "LoadCategory"
                    If field(0) = "Category" Then
                        cboCategory.Items.Add(field(1))
                        cboCategory.SelectedIndex = 0 ' Auto Select first Category.
                    End If

                Case "LoadUnits"
                    If field(0) = CStr(cboCategory.SelectedItem) Then
                        cboConvertTo.Items.Add(field(1))
                        cboConvertTo.SelectedIndex = 0 ' Auto Select first Unit.
                    End If

                Case "SelectUnit"
                    If field(1) = CStr(cboConvertTo.SelectedItem) Then
                        UnitConvVal = CDbl(field(2)) ' Load Unit's Conversion value, store in UnitConvVal as Double.
                    End If
            End Select
        Next
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Me.Load
        DataLoad("LoadCategory") ' Switch to DataLoad to load Categories on form load.
    End Sub

    Private Sub cboCategory_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cboCategory.SelectedIndexChanged
        cboConvertTo.Items.Clear() ' Clear cboConvertTo Combobox when re-loading units after selection change.
        DataLoad("LoadUnits")
    End Sub

    Private Sub cboConvertTo_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cboConvertTo.SelectedIndexChanged
        DataLoad("SelectUnit")
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalculate.Click
        If txtInputVal.Text = Nothing Then
            MessageBox.Show("Please Enter A Value to Convert") ' Display message if no value is entered.
        Else
            txtResult.Text = CStr(CDbl(txtInputVal.Text) * UnitConvVal) ' If Value has been entered, compute conversion for unit.
        End If
    End Sub
End Class

Now I am getting an error of IndexOutOfRangeException was unhandled. What happened for that to come up and how do I fix it?

Hi,
The only place you're using an integer that cause the out of range exception is when you refer to field(1) or field(2). So I would check that your field, when split on the comma character actually has 3 resulting splits e.g. 2 commas are in the initial line.
Otherwise, if your line was "hello, goodbye" for example, there would be no field(2), just field(0) and field(1).
Hope that helps,