Just to finish-up from yesterday. My experiments show that SharpZipLib and DotNetZip produce compatible zip files that can be processed by PKZIP and WinZip, so long as you're not using strong encryption (that result is expected of course, otherwise someone's deflate code is wonky and that would have been discovered by now).
As we seem to agree, the DotNetZip library is friendlier for developers to consume and it seems to have more features. Only SharpZipLib has Silverlight support at the moment, but the DotnetZip home page says it's coming in the next release. I'm sticking to DotNetZip from now on. Now once you get into strong encryption things get messy for .NET developers. I have proof that PKZIP and WinZip files are not compatible if you use strong encryption. Some historical articles I found lament this back in 2003 when WinZip diverged with an arguably non-standard format. Since then they compromised a bit and their products have unzip support for each other. It seems that the WinZip format is ahead in the popularity polls because of its open documentation. PKZIP can encrypt files with a variety of strong algorithms (including AES), and it looks like no one but PKZIP can read them back again. This applies to my backups in the cloud, which is a worry! So if you want to manipulate strongly encrypted zip files in managed code then it looks like WinZip and the DotNetZip library (with AES only) are the only useful combinations I can find. All of my future backups will be in this format and I might even delete PKZIP. Greg P.S. I downloaded WinZip 15 eval copy on a spare VM so I could sanity check my files. Holey schmoley! What a load of bloated crapware WinZip has become since I last saw it many years ago. It looks like it was created by a dyslexic colour-blind school kid with too much hobby time.
