Public Function CheckIfFileIsFree (ByVal Dateiname As String) As Boolean
 
Dim Datei_verfuegbar As Boolean
 
Dim fs As FileStream 
fs = New FileStream(Dateiname, FileMode.Open, FileAccess.ReadWrite, _
  FileShare.None)
Dim sr As StreamReader
 
Do
  Datei_verfuegbar = True
 
  Try
     sr = New StreamReader(fs)
     sr.close()
  Catch ex As IOException
     Datei_verfuegbar = False  'Datei gesperrt
  Catch ex As Exception
     msgbox(ex.Message, MsgBoxStyle.Exclamation)  'andere Fehler melden 
  End Try
 
  Thread.Sleep(100) 'kurz warten
 
Loop Until Datei_verfuegbar = True
 
' Aufräumen
sr.dispose()
 
Return Datei_verfuegbar
 
End Function