WinapiServer::DeleteFile

hello!!

i have a problem to use a Winapi::DeleteFile in a Batch in Ax 2012.

This is my code:

FileIOPermission            sourceFileWritePerm;

.....................................

 CodeAccessPermission::revertAssert();
  sourceFileWritePerm = new FileIOPermission(filename, #io_write);
  sourceFileWritePerm.assert();
  WinAPIServer::deleteFile(filename);
  CodeAccessPermission::revertAssert();

but the file is not deleted:(

Why??? i don't understand!!!

Thanks for help me,

Antonio