void ExtractZipFile (string zipFile, string outDir)
{
ZipInputStream zip = new ZipInputStream (File.OpenRead (zipFile));
ZipEntry entry;
while ((entry = zip.GetNextEntry ()) != null) {
string file = Path.Combine (outDir, entry.Name);
Directory.CreateDirectory (Path.GetDirectoryName (file));
using (var output = File.OpenWrite (file))
zip.WriteTo (output);
}
}