Nobody said that Unity3 will ship with a mono that has a fully managed GZipStream implementation. In fact, being the guy that is working on this currently, I can tell you that that would be extremely unlikely. So yes, also for the Unity3.0 timeframe, you'll have to rely on a managed implementation.

I went and tried the 3rd party library you are having trouble with: DotNetZip. I downloaded their distribution package, and grabbed Ionic.Zip.dll from it, and placed it into the Assets folder of an empty Unity2.6.1 project.

I then wrote a quick testscript:

using UnityEngine;
using Ionic.Zip;

public class NewBehaviourScript : MonoBehaviour {
    // Use this for initialization
    void Start () {
        using (ZipFile zip = new ZipFile())
        {
             // add this map file into the "images" directory in the zip archive
             zip.AddFile("c:\\mono.patch", "images");
             // add the report into a different directory in the archive
             zip.Save("MyZipFile.zip");
        }
    }
}

(copied almost verbatim from their website). c:\mono.patch is a file that happened to live in my c:\ drive. When I ran this script, it succesfully wrote MyZipFile.zip.

Naturally the .AddFile() won't work from a webplayer, but this library has entrypoints for creating new files in the zipfile from a stream as well.

If this does not work for you, please describe the exact steps you're taking, and the exact error you get.

Have you tried looking at 7Zip? Has a completely managed C# library that I know works in Unity. It gives you compress/uncompress to and from memory streams/byte arrays, in LZMA format, so it's better than zip and actually what Unity uses to compress assets.

http://www.7-zip.org/sdk.html

If you need something compatible with .zip format you might have some trouble.

I've been trying to extract a zip to a stream. It works great in the editor. The webplayer doesn't seems to work though. Are there known issues with the webplayer when using the DotNetZip implementation?

Potential Answer: SharpZipLib

There has been no progress on this question so I will post my research into this potential answer.

http://www.icsharpcode.net/opensource/sharpziplib/

The current version of SharpZipLib seems to work. Code will compile and run in the Unity editor. But the same problem with DotNetZip arises:

NotSupportedException: CodePage 437 not supported

is thrown when the project is built and running on the mono bits.

Another SharpZipLib/Unity developer banged his head on the wall last year and was able to get the code to work with the Unity version of the SharpZipLib library: http://community.sharpdevelop.net/forums/p/9762/27065.aspx

His bug demo code was still posted, so I grabbed the .dll from it and used it in my code. It WORKS! But, I won't immediately call this an acceptable answer to this question. This is the version of the library that ships with Unity (located here: Unity\Editor\Data\Frameworks\Mono.framework), so whatever bugfixes or improvements may have happened after this version was published, or may happen in the future, are lost to me.

This is the closest answer yet, but we're still not there yet. If others post their experiences with this solution, then I may feel better about calling this the answer.

Bit of an update -

Both Ionic.Zlib and Ionic.Gzip work great on Unity 3.5.3 for Window / mac editor. This does not include the

I began to have issues when I compiled for the I18N*.dll assemblies discussed above.

When I compiled to the iPhone, the error mentioned at the top occurred: "IBM437 codepage not supported"

I attempted to bring all the I18N*.dll's over, and I got the error that I18N.Rare.dll could not be cross compiled with AOT.

I then deleted that file and attempted again - and everything worked great.

So as for Unity 3.5.3 - You could bring in all I18N* files, but do not include the I18N.Rare.dll.

Thanks for this post - it was very helpful.