StreamReader problem

I need to find out how to display the last 128 characters of a text document. I've tried using StreamReader to get the whole file but I only need the last 128 characters. Here is my code so far:

<VB.NET 2005>

Private Sub Button12_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button12.Click

If ListBox1.Text = "" Then

MessageBox.Show("No File Selected", "Error")

Exit Sub

End If

Dim sr As New System.IO.StreamReader(ListBox1.Text)

Dim WholeFile As String = sr.ReadToEnd()

Dim LastDigits As String = ""

Dim Index As Integer

If WholeFile.Length > 128 Then

For Index = WholeFile.Length - 128 To WholeFile.Length - 1

LastDigits = LastDigits & WholeFile(Index)

Next

MessageBox.Show(LastDigits, "Test")

End If

End Sub

</VB.NET 2005>

It doesn't display the data correctly, only the first few words and it doesn't display several blankspaces " " as is in the file.

Can somebody please help... Thanks in advance.

Answer this question

StreamReader problem

Jim Kelly
ID3 tags sometimes use C-style (ASCII 0-terminated) strings and are thus binary data -- you can't treat them as VB.NET strings without running into all kinds of issues.

Something like the following should work:

        Dim sr As New System.IO.StreamReader("YourFile.mp3")
        Dim br As New System.IO.BinaryReader(sr.BaseStream)
        sr.BaseStream.Seek(-128, IO.SeekOrigin.End)
        Dim b() As Byte = br.ReadBytes(128)
        If GetString(b, 0, 3) <> "TAG" Then
            Throw New Exception("No ID3v1 tag found")
        End If

        Dim Title As String = GetString(b, 3, 30)
        Dim Artist As String = GetString(b, 33, 30)
        Dim Album As String = GetString(b, 63, 30)
        Dim Year As String = GetString(b, 93, 4)
        Dim Comment As String = GetString(b, 97, 30)
        Dim Genre As Byte = b(127)

(don't forget to close sr and br)

    Private Function GetString(ByVal b() As Byte, ByVal StartOffset As Integer, ByVal MaxLen As Integer) As String
        Dim res As String = ""
        For i As Integer = StartOffset To StartOffset + MaxLen - 1
            If b(i) = 0 Then
                Exit For
            Else
                res &= Chr(CInt(b(i)))
            End If
        Next i
        Return res.Trim
    End Function

'//mdb
Bill Nortman

Thanks,

It's an MP3 file and I want to retrieve the ID3v1 tag which is in the last 128 digits. This brings up the same string in a messagebox as my code. This is a lot shorter than my code though :)

It only brings up "TAG{Title}" then nothing...

Do I need to convert the string or something

Thanks again,
cin_ful
You don't specify the exact file format, but something like the following should work for pure text files:

Dim sr As New System.IO.StreamReader("YourFileNameHere")
sr.BaseStream.Seek(-128, IO.SeekOrigin.End)
Dim LastDigits As String = sr.ReadToEnd()

'//mdb
SteveMeyns

mdb,
Thanks for the help. That works like a dream. Cheers,
StreamReader problem

Answer this question