Unzip files programmatically in .net

We have used SharpZipLib successfully on many projects. I know it's a third party tool, but source code is included and could provide some insight if you chose to reinvent the wheel here.

With .NET 4.5 you can now unzip files using the .NET framework:

using System;
using System.IO;

namespace ConsoleApplication
{
  class Program
  {
    static void Main(string[] args)
    {
      string startPath = @"c:\example\start";
      string zipPath = @"c:\example\result.zip";
      string extractPath = @"c:\example\extract";

      System.IO.Compression.ZipFile.CreateFromDirectory(startPath, zipPath);
      System.IO.Compression.ZipFile.ExtractToDirectory(zipPath, extractPath);
    }
  }
}

The above code was taken directly from Microsoft's documentation: http://msdn.microsoft.com/en-us/library/ms404280(v=vs.110).aspx

ZipFile is contained in the assembly System.IO.Compression.FileSystem. (Thanks nateirvin...see comment below). You need to add a DLL reference to the framework assembly System.IO.Compression.FileSystem.dll

Free, and no external DLL files. Everything is in one CS file. One download is just the CS file, another download is a very easy to understand example. Just tried it today and I can't believe how simple the setup was. It worked on first try, no errors, no nothing.

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

For .Net 4.5+

It is not always desired to write the uncompressed file to disk. As an ASP.Net developer, I would have to fiddle with permissions to grant rights for my application to write to the filesystem. By working with streams in memory, I can sidestep all that and read the files directly:

using (ZipArchive archive = new ZipArchive(postedZipStream))
{
    foreach (ZipArchiveEntry entry in archive.Entries)
    {
         var stream = entry.Open();
         //Do awesome stream stuff!!
    }
}

Alternatively, you can still write the decompressed file out to disk by calling ExtractToFile():

using (ZipArchive archive = ZipFile.OpenRead(pathToZip))
{
    foreach (ZipArchiveEntry entry in archive.Entries)
    {
        entry.ExtractToFile(Path.Combine(destination, entry.FullName));
    }
} 

To use the ZipArchive class, you will need to add a reference to the System.IO.Compression namespace and to System.IO.Compression.FileSystem.