Call this method to get the size in bytes of the file.
HRESULT GetSize(
   ULONGLONG& nLen 
) const throw( );
Parameters
- nLen
 The number of bytes in the file.
Return Value
Returns S_OK on success, or an error HRESULT on failure.
Remarks
Calls GetFileSize to get the size in bytes of the file.
Requirements
Header: atlfile.h