DLLVERSIONINFO dvi = new DLLVERSIONINFO ();
dvi.cbSize = (uint)System.Runtime.InteropServices.Marshal.SizeOf (dvi);
int resultado = DllGetVersion (ref dvi);

if (resultado == 0)
  return string.Format ("{0}.{1}.{2}", dvi.dwMajorVersion, dvi.dwMinorVersion, dvi.dwBuildNumber);
else
  return "?";