Hello Dave,
From your post, my understanding on this issue is: you want to know how to
determine the file type (docx/xlsx) according to a file stream. If I'm off
base, please feel free to let me know.
In the previous versions of Office file types, in order to determine the
file type according to the file stream, we could utilize the file signature
information in the first few bytes of the stream. (See File Signature Table
http://www.garykessler.net/library/file_sigs.html). But in Office 2007,
because all the files are actually in zip format, I do not think that we
could rely on the file signature.
Based on my discussion with Office product team, Office 2007, internally,
is mainly depending on the file extension to determine the file type due to
some security issues. For instance, if you rename a xlsx file to docx,
Office would choose to use Word, rather than Excel, to open the file even
if the file format is xlsx actually.
For your question about how to determine the file type with just a file
stream, I think we do need to extract the [Content_types].xml with, for
instance, SharpZipLib. Then check the Content Type items.
For docx file:
<Override PartName="/word/document.xml"
ContentType="application/vnd.openxmlformats-officedocument.wordprocessingml.
document.main+xml" />
For xlsx file:
<Override PartName="/xl/workbook.xml"
ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.she
et.main+xml" />
Please let me know if you have any other concerns, or need anything else.
Sincerely,
Jialiang Ge (
[email protected], remove 'online.')
Microsoft Online Community Support
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