Visual Basic Parsing - visual-studio-2010

Question

Ok so I'm working on a program that parses input in the textbox and finds a delimiter such as a comma, space, or a line pressed using enter key and extracting each word before each delimiter and posting it in the listbox. I keep getting errors though.
Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
Dim delimiter As String = ""
Dim oldIndex As Integer = 0
Dim newIndex As Integer = 0
Dim length As Integer = 0
Dim tempString As String = ""
Dim tempWord As String = ""
Dim advanceSize As Integer = 0
If RadioButton1.Checked = True Then
delimiter = ","
advanceSize = 1
tempString = TextBox1.Text
length = tempString.Length
Do While oldIndex < length
newIndex = tempString.IndexOf(delimiter)
tempWord = Mid(tempString, oldIndex, newIndex)
tempWord.Trim()
oldIndex = newIndex + advanceSize
ListBox1.Items.Add(tempWord)
Loop
ElseIf RadioButton2.Checked = True Then
delimiter = vbCrLf
advanceSize = 2
tempString = TextBox1.Text
length = tempString.Length
Do While oldIndex < length
newIndex = tempString.IndexOf(delimiter)
newIndex = tempString.IndexOf(delimiter)
tempWord = Mid(tempString, oldIndex, newIndex)
tempWord.Trim()
oldIndex = newIndex + advanceSize
ListBox1.Items.Add(tempWord)
Loop
ElseIf RadioButton3.Checked = True Then
delimiter = " "
advanceSize = 1
tempString = TextBox1.Text
length = tempString.Length
Do While oldIndex < length
newIndex = tempString.IndexOf(delimiter)
newIndex = tempString.IndexOf(delimiter)
tempWord = Mid(tempString, oldIndex, newIndex)
tempWord.Trim()
oldIndex = newIndex + advanceSize
ListBox1.Items.Add(tempWord)
Loop
Else
Exit Sub

Answer 1

In the first line read, the value of oldindex is zero. The Mid function requires a number greater than zero for the second parameter because, unlike the string.substring method, it is one-based rather than zero-based. The error will be resolved if you initialize oldindex to 1.
Incidentally, the third parameter of mid (and .substring) is length, not an ending index.

Answer 2

May I suggest an alternative which achieves the goal of your question? There is a String.Split function which you can use. It's a bit fiddly, as to split on a string you need to use an array of strings (there can be just one in the array, which is all we need) and you have to specify a StringSplitOptions value, but apart from that it is easy to use:
Private Sub bnSplitData_Click(sender As Object, e As EventArgs) Handles bnSplitData.Click
Dim txt = tbDataToSplit.Text
Dim delimiter As String() = Nothing
' select case true is an easy way of looking at several options:
Select Case True
Case rbCommas.Checked
delimiter = {","}
Case rbNewLines.Checked
delimiter = {vbCrLf}
Case rbSpaces.Checked
delimiter = {" "}
Case Else ' default value
delimiter = {","}
End Select
Dim parts = txt.Split(delimiter, StringSplitOptions.RemoveEmptyEntries)
' get rid of the old entries
ListBox1.Items.Clear()
' add the new entries all in one go
ListBox1.Items.AddRange(parts)
End Sub
Please note how I gave the controls (except ListBox1) meaningful names - it makes referring to the correct one much easier.