Open ZIP Package from MemoryStream

Question

I want to handle the contents of a ZIP file, that was downloaded, only into memory (without using the hard disk!). packageStream contains the bytes of the ZIP file.

MemoryStream packageStream = // Stream of downloaded ZIP file    
var zipPackage = System.IO.Packaging.Package.Open(packageStream, FileMode.Open, System.IO.FileAccess.Read);
var parts = zipPackage.GetParts();
var rels = zipPackage.GetRelationships();

parts and rels do not contain any items.

Can anybody tell me what I'm doing wrong?

Is a MemoryStream the wrong stream type?

Is the Package class the wrong class for ZIP files in this scenario?

If you can tell me any alternatives, please no third party projects.

Thanks!

UPDATE

This answer in the duplicated question solved my problem (ZipArchive class). The accepted answer uses a third party project.

Have you tried this? https://stackoverflow.com/a/21767078/3596441 — The One, Jan 19 '18 at 14:03
_"Is a MemoryStream the wrong stream type?"_ Why not just save it to the file and then try to open it (for test purposes only)? — Aleks Andreev, Jan 19 '18 at 14:03

score 1 · Accepted Answer · answered Jan 19 '18 at 14:13

How you can handle .zip files, depends on the Framework version you are using. Streams are fully interchangeable and can even encapsulate one another. The question is if you have a class that can actually take a stream and do zip Operations.

If you have at least Framework 4.5, you got the ZipArchive class and this whole thing is childsplay. The examples take a Stream and it can be any implemention of the Stream abstract class. All that memory stream is, is a readyonly stream.

If you are under that, I am pretty sure you are hosed. There simply is no class that can take a Stream and do ZIP operations on it before 4.5. Most approaches invovle saving the .zip file on the disk and decompressing it using a console programm with IO redirection. Both Windows ZIP functionaltiy and 7zip work for that, but both involve writing on the Disk.

Perhaps you can use the code part of 7-zip to do a in-process/in memory zip operation. But that might be a tricky.

ZipArchive class did it... Thanks! – Christian St. Jan 19 '18 at 14:29 — Christian St., Jan 19 '18 at 14:29

Open ZIP Package from MemoryStream

1 Answers1