Streamreader - Object reference not set to an instance of an object

Hi
I have the following code in a button click event
Dim sr As StreamReader
        Dim sw As New StreamWriter(btnSWFolder.Text & "\" & lstSWFiles.Text, True)
        Dim sLine As String = ""
        Dim sDiv As String = ""

        For Each subor As String In My.Computer.FileSystem.GetFiles(btnSRFolder.Text)
            Try
                sr = New StreamReader(subor)
                Do
                    sLine = sr.ReadLine()
                    If sLine.StartsWith("ORDER JOURNAL") Then
                        sDiv = Mid(sLine, 57, 2)
                        sw.WriteLine(sDiv)
                    End If
                Loop Until sLine Is Nothing
                sr.Close()
            Catch ex As Exception
                MessageBox.Show(ex.Message)
            End Try
        Next
        sw.Close()
    End Sub

streamreader reads the string (sDiv) and the streamwriter attaches it to a text file. Everything works fine. Only if it hadn't been for that annoying message : Object reference not set to an instance of an object.
When I removed Try ... Catch, VB Studio 2005 stopped and highlighted the line
     If sLine.StartsWith("ORDER JOURNAL") Then
and the explanatory note than gopes underneath showed in the blue bar the following:
    NullReferenceException was unhandled

What's wrong? Why do I get the message when everything works fine?
Thanks
Fero
LVL 6
Fero45Asked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

jeepstyx22Commented:
Post below obtained from (8th post down): http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=1053653&SiteID=1

The problem is as follows:
streamReader.ReadLine will return a null reference (Nothing) at the end of the stream.
You then try to evaluate reader.StartsWith(...) when reader is a null reference.
So you need to check for a null reference (Nothing) before attempting to evaluate reader.StartsWith(...).
There are several ways of doing this, for example:            

Do Until reader Is Nothing OrElse reader.StartsWith("Job Log")
...
Loop

 
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
Fero45Author Commented:
Hi jeepstyx22:
I accepted your answer, thanks. But I have a similar code and never get that message, Just for info
Dim sr As StreamReader
        Dim sw As StreamWriter
        Dim sRadek As String = ""
        Dim sezona As String = ""
        Dim farba As String = ""
        Dim sDiv As String = ""
        Dim subdiv As String = ""
        Dim sDatum As String = ""

        Try
            sw = New StreamWriter(btnSWFolder.Text & "\" & lstSWFiles.Text, True)
            sr = New StreamReader(btnSRFolder.Text & "\" & lstSRFiles.Text)

            Do
                sRadek = sr.ReadLine()

                If sRadek.StartsWith("Output") Or _
                    sRadek.Length = 0 Or sRadek.StartsWith("STYL") Or _
                    sRadek.StartsWith("*") Then
                    'skip

                ElseIf sRadek.StartsWith("BOOKING") Then
                    sDiv = Mid(sRadek, 40, 2)

                ElseIf sRadek.StartsWith("DATE") Then
                    sDatum = Mid(sRadek, 7, 8)

                Else
                    subdiv = fn_div_subdiv(sDiv, Mid(sRadek, 1, 4))
                    sezona = fn_carry_spring07_other(Mid(sRadek, 1, 4))

                    If sezona = "Other" Then
                        'skip
                    Else
                        farba = fn_farba(Mid(sRadek, 7, 2))
                        sw.WriteLine(sDatum & "=" & subdiv & "=" & Mid(sRadek, 1, 4) & "=" & _
                                        farba & "=" & Mid(sRadek, 10, 6) & "=" & _
                                        Trim(Mid(sRadek, 18, 4)) & "=" & Trim(Mid(sRadek, 23, 4)) & "=" & _
                                        Trim(Mid(sRadek, 28, 4)) & "=" & Trim(Mid(sRadek, 33, 4)) & "=" & _
                                        Trim(Mid(sRadek, 38, 4)) & "=" & Trim(Mid(sRadek, 43, 4)) & "=" & _
                                        Trim(Mid(sRadek, 48, 4)) & "=" & Trim(Mid(sRadek, 53, 4)) & "=" & _
                                        Trim(Mid(sRadek, 58, 4)) & "=" & Trim(Mid(sRadek, 63, 4)) & "=" & _
                                        Trim(Mid(sRadek, 68, 4)) & "=" & Trim(Mid(sRadek, 76, 4)) & "=" & _
                                        sezona)
                    End If

                End If
            Loop Until sRadek.Contains("R A N K    B Y    S T Y L E")

            sr.Close()
            sw.Close()
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
        MessageBox.Show(sDiv & " done!")

Thanks
Fero
0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Visual Basic.NET

From novice to tech pro — start learning today.