求教：MINI中获得文件长度

是这样，需求是得到这个文件的MD5 CODE，可是这就需要得到文件长度。
找到一个函数  
FltQueryInformationFile(
    IN PFLT_INSTANCE  Instance,
    IN PFILE_OBJECT  FileObject,
    OUT PVOID  FileInformation,
    IN ULONG  Length,
    IN FILE_INFORMATION_CLASS  FileInformationClass,
    OUT PULONG  LengthReturned OPTIONAL
    )
可是参数FileInformationClass有如下选择项:
Type of file information to be returned. One of the following. Value Meaning
FileAllInformation Return a FILE_ALL_INFORMATION structure for the file.  
FileAttributeTagInformation Return a FILE_ATTRIBUTE_TAG_INFORMATION structure for the file.  
FileBasicInformation Return a FILE_BASIC_INFORMATION structure for the file.  
FileCompressionInformation Return a FILE_COMPRESSION_INFORMATION structure for the file.  
FileEaInformation Return a FILE_EA_INFORMATION structure for the file.  
FileInternalInformation Return a FILE_INTERNAL_INFORMATION structure for the file.  
FileMoveClusterInformation Return a FILE_MOVE_CLUSTER_INFORMATION structure for the file.  
FileNameInformation Return a FILE_NAME_INFORMATION structure for the file.  
FileNetworkOpenInformation Return a single FILE_NETWORK_OPEN_INFORMATION structure for the file.  
FilePositionInformation Return a single FILE_POSITION_INFORMATION structure for the file.  
FileStandardInformation Return a single FILE_STANDARD_INFORMATION structure for the file.  
FileStreamInformation Return a single FILE_STREAM_INFORMATION structure for the file.  

不止一个选项能够返回不止一个长度，我应该用哪一个？请各位大牛多指教。多谢！

FILE_STANDARD_INFORMATION 不就可以吗？

用返回结构中的EndOfFile，这应该就是文件长度。