Public Function ReplaceCharInFile(ByVal Datei As String, ByVal OldChar As _
      String, ByVal NewChar As String) As Boolean
        Try
            Dim SR As New IO.StreamReader(Datei)
            Dim OldGesamteDatei As String = ""
            Dim NewGesamteDatei As String = ""
            OldGesamteDatei = SR.ReadToEnd
            SR.Close()
 
            NewGesamteDatei = Replace(OldGesamteDatei, OldChar, NewChar)
 
            Dim SW As New IO.StreamWriter(Datei, False)
            SW.Write(NewGesamteDatei)
            SW.Close()
 
            Return True
        Catch ex As Exception
            MsgBox(ex.Message, MsgBoxStyle.Exclamation, ex.Source)
            Return False
        End Try
    End Function