Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button3.Click
        Dim folder As String = InputBox("Zielverzeichnis")
        Dim sr As New System.IO.StreamReader("C:\files")
        Dim sw As New System.IO.StreamWriter("C:\files_prev")
        Dim thumbnailcounter As Integer = 0
 
 
 
        Dim file As String
        Dim image As System.Drawing.Image
        Dim thumbnail As System.Drawing.Image
        While Not sr.EndOfStream
            file = sr.ReadLine
            image = System.Drawing.Image.FromFile(file)
            thumbnail = image.GetThumbnailImage(160, 120, Nothing, New IntPtr())
 
            Dim filename As String = file
            filename = Microsoft.VisualBasic.Right(filename, Len(filename) - _
              filename.LastIndexOf("\") - 1)
            filename = Microsoft.VisualBasic.Left(filename, Len(filename) - _
            filename.LastIndexOf(".") - 1)
            filename = folder & "\" & filename & "_prev" & thumbnailcounter & _
            ".jpg"
            thumbnailcounter = thumbnailcounter + 1
 
            thumbnail.Save(filename, System.Drawing.Imaging.ImageFormat.Jpeg)
            sw.Write(filename & vbCrLf)
 
        End While
        sw.Close()
 
        MsgBox("process finnished")
    End Sub