Any Suggestions for Making this More Efficient?

I'd like to see if anyone has any suggestions on making the following function faster or more efficient. This code segment reads data from a CVS file, breaks it up and writes the relevant data to a flat file. Some sample input would be:

Column A Column B
004-005 5
35 6
010-034 5

VB Code:

Private Function createzonesFedEx(ByVal Filename As String, ByVal ShipType As String, ByVal Carrier As String)
        Dim dash As Boolean 'determines whether or not the first column of numbers contain a dash
        Dim i As Integer
        Dim line As String 'line of data to be read
        Dim commaArray() As String 'array of strings delimited by commas
        Dim dashArray() As String ' array of strings delimited by dashes
        Dim sr = New System.IO.StreamReader(Filename) ' I/O object to read data from Filename
        Dim sw = New System.IO.StreamWriter(FILEPATH, True) 'I/O object to write data to FILEPATH
 
        line = sr.readline
        While Not line Is Nothing
 
            commaArray = Split(line, ",")
 
            If (Mid(commaArray(0), 4, 1) = "-") Then
                dashArray = Split(commaArray(LBound(commaArray)), "-")
                dash = False
            Else
                dash = True
            End If
 
            For i = 0 To 7 Step 1
                Me.cboShipType.SelectedIndex = i
                Try
                    sw.write(FRFIRM)
                    sw.write(",")
                    sw.write(Me.cboCarrier.Text)
                    sw.write(",")
                    sw.write(Me.cboShipType.Text)
                    sw.write(",")
                    sw.write(FVRSN)'Global constant
                    sw.write(",")
                    If (dash = False) Then
                        sw.write(Format(Val(Trim(dashArray(0))), "000"))
                        sw.write(",")
                        sw.write(Format(Val(Trim(dashArray(1))), "000"))
                        sw.write(",")
                        sw.write(Format(Val(Trim(dashArray(1))), "000"))
                    Else
                        sw.write(Format(Val(Trim(commaArray(0))), "000"))
                        sw.write(",")
                        sw.write(Format(Val(Trim(commaArray(0))), "000"))
                        sw.write(",")
                        sw.write(Format(Val(Trim(commaArray(0))), "000"))
                    End If
                    sw.write(",")
                    sw.write(FRSTA)'Global constant
                    sw.write(",")
                    sw.write(Now.Today.ToString("yyyyMMdd"))
                    sw.write(",")
                    sw.write(Now.Today.ToString("yyyyMMdd"))
                    sw.write(",")
                    sw.write(FRZAEN)'Global constant
                    sw.write(",")
                    sw.write(FRUSER)'Global constant
                    sw.write(",")
                    sw.writeline(FRWSID)'Global constant
                    sw.newline()
                Catch ex As Exception
                    MessageBox.Show(ex.Message)
                End Try
            Next
            line = sr.readline
        End While
        Me.cboShipType.SelectedIndex = -1
        sw.Close()
    End Function

This works fine, I just think it could be done better. Any suggestions? Thank you for your time.

It didn't turn out quite like I wanted it to, so to clarify: Column A is the 004-005, 35, 010-034 and Column B is 5,6,5.

What's the problem with it? I can see a few simple little changes that might save the blink of an eye, but nothing that would save considerable time.

I have a few suggestions.
1. If the input csv file isn't too big, try read the whole file to memory at once.
2. Why you have to loop thru 0-7 and set the combobox's selectedindex for every line in the csv file just to read its text?
3. Use stringbuilder to build your output, then once all done, write it to the output file.

Actually, changing the index on the comboboxes was the one thing which I thought might make a significant improvement. It would be better to just get the items from the combobox directly rather than making it the selected index, then getting the selected item. However, I don't know whether or not that would make a noticeable improvement in speed.

Read the whole file into memory by splitting line by line

VB Code:

Dim sr As New System.IO.StreamReader("filename")
        Dim str As String = sr.ReadToEnd()
        'this will split each line and put it in memory 
        Dim strAry() As String = str.Replace(Chr(10), "").Split(Chr(13))

This takes away having to call ReadLine() over and over.

The easiest thing to do would just append that text to a System.Text.StringBuilder and then write the whole thing to the writer at the end instead of hitting it every line.