推荐一个操作Zip文件的开源类库：DotNetZip

using (ZipFile zip = new ZipFile())   
{   
    zip.Password = sPassword; //set pwd
    zip.AddDirectory(sZipDir);   
    zip.Save(sSavePath + @"\" + sSaveName);   
}

using (ZipFile zip = new ZipFile("Backup.zip"))
  {
    zip.Password= "123456!";
    zip.AddFile("ReadMe.txt");
    zip.AddFile("7440-N49th.png");
    zip.AddFile("2005_Annual_Report.pdf");        
    zip.Save();
  }

using (ZipFile zip = ZipFile.Read("D:\\test\\2007.zip"))
{
    foreach (ZipEntry e in zip)
    {
        Console.WriteLine("file name:{0}", e.FileName);
        Console.WriteLine(e.Comment);
        e.Extract("D:\\test\\pwdata", true);  // overwrite == true
    }
}