CODEWITHSUNDEEP
c#.netzip
bassist
bassist

Reputation: 75

Create Uncompressed Zip in C#

I have a question according to the ZipArchive Library in System.IO.Compression. I want to create an uncompressed .zip file. My code so far looks like this:

//Creates a "Deflate"-Mode file in the created zip.
using (FileStream fs = new FileStream(zippath, FileMode.OpenOrCreate))
using (ZipArchive zip = new ZipArchive(fs, ZipArchiveMode.Update))
{
    var demoFile = zip.CreateEntry("foo0.txt", CompressionLevel.NoCompression);  //NoCompression does not seem to have an impact
    using (var streamWriter = new StreamWriter(demoFile.Open()))
    {
        streamWriter.Write("Bar!");
    }
}

Thats creating me a zip file, where the file in it was written in "DEFLATE" Mode not in STORE. How can I fix this. My thought was, my problem would be solved by using the CompressionLevel.NoCompression.

Also writing the file to the filesystem and zipping the directory is not an option, because i want to create a zipfile with potentially hundred of thousands small files. Furthermore just using GZipStream is not an option, because I want to create a directory structure in the .zip file.

I checked the mode with 7-zip:

(screenshot from 7-zip)

Upvotes: 2

Views: 2804

Answers (2)

Xero
Xero

Reputation: 51

For anyone who happens to see this topic later on, I would highly recommend the ZipStorer class by Jaime Olivares:

https://github.com/jaime-olivares/zipstorer

It's easy to add this code to a C# project (not a DLL), and it's easy to add files using 'store' instead of 'deflate'.

Upvotes: 2

amain
amain

Reputation: 1688

If for whatever reason you are required to add contents to a ZIP file with its compression method explicitly set to STORE (no compression), you will need to use some third party library.

The .NET classes in System.IO.Compression use DEFLATE by default. There is no apparent way to change this and use another compression method or algorithm.
Providing CompressionLevel.NoCompression just tells the DEFLATE algorithm to work with the lowest compression rate1. In terms of file size, this will probably give you roughly the same end result, anyway.

Third party libraries supporting the method STORE include:

1 which should be... no compression. See DEFLATE's non-compressed blocks

Upvotes: 4

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