Decompressing password-protected ZIP files with .NET 4.5

As pointed out, DotNetZip is your friend. Unpacking your zip file is as easy as

using ( ZipFile archive = new ZipFile( @"c:\path\to\your\password\protected\archive.zip",) )
{
  archive.Password = "your-pass-word-here" ;
  archive.Encryption = EncryptionAlgorithm.PkzipWeak ; // the default: you might need to select the proper value here
  archive.StatusMessageTextWriter = Console.Out;

  archive.ExtractAll( @"c:\path\to\unzip\directory\", ExtractExistingFileAction.Throw ) ;
}

In my experience, DotNetZip runs about as fast as Info-Zip's open source unzip utility and uses roughly the same amount of memory.

---

Edited To Note: DotNetZip used to live at Codeplex. Codeplex has been shut down. The old archive is still available at Codeplex. It looks like the code has migrated to Github:

• https://github.com/DinoChiesa/DotNetZip. Looks to be the original author's repo.
• https://github.com/haf/DotNetZip.Semverd. This looks to be the currently maintained version. It's also packaged up an available via Nuget at https://www.nuget.org/packages/DotNetZip/

---

Unfortunately not. There is no support within the .Net Framework 4.5 for password protected zip files. In this case you have to switch to one of the well known 3rd party libraries.