How to compress/decompress directories using GZipStream

My alternative is to rather use a tried and tested compression api. It's simpler to use and you don't have to spend time developing helper methods to zip and unzip files.
http://dotnetzip.codeplex.com/[^]

Create a zip file

using (ZipFile zip = new ZipFile())
 {
   zip.AddFile("ReadMe.txt");
   zip.AddFile("7440-N49th.png");
   zip.AddFile("2008_Annual_Report.pdf");
   zip.Save("Archive.zip");
 }

Extract a zip file

private void MyExtract()
  {
      string zipToUnpack = "C1P3SML.zip";
      string unpackDirectory = "Extracted Files";
      using (ZipFile zip1 = ZipFile.Read(zipToUnpack))
      {
          // here, we extract every entry, but we could extract conditionally
          // based on entry name, size, date, checkbox status, etc.  
          foreach (ZipEntry e in zip1)
          {
            e.Extract(unpackDirectory, ExtractExistingFileAction.OverwriteSilently);
          }
       }
    }

Create a downloadable zip within asp.net

public void btnGo_Click (Object sender, EventArgs e)
{
  Response.Clear();
  Response.BufferOutput= false;  // for large files
  String ReadmeText= "This is a zip file dynamically generated at " + System.DateTime.Now.ToString("G");
  string filename = System.IO.Path.GetFileName(ListOfFiles.SelectedItem.Text) + ".zip";
  Response.ContentType = "application/zip";
  Response.AddHeader("content-disposition", "filename=" + filename);
  
  using (ZipFile zip = new ZipFile()) 
  {
    zip.AddFile(ListOfFiles.SelectedItem.Text, "files");
    zip.AddEntry("Readme.txt", "", ReadmeText);
    zip.Save(Response.OutputStream);
  }
  Response.Close();
}

as well as various other uses.