' Change the extension of a file name' if the last argument is True, it adds the extension even if the file doesn't ' have oneFunction ChangeFileExtension(ByVal FileName As String, _    ByVal Extension As String, Optional ByVal AddIfMissing As Boolean = False) _    As String    If AddIfMissing OrElse IO.Path.GetExtension(FileName).Length > 0 Then        Return IO.Path.ChangeExtension(FileName, Extension)    Else        Return FileName    End IfEnd Function