private void NestedArchiveExample( Stream someStream )
{
  using( ZipWriter writer = new ZipWriter( someStream ) )
  {
    ZipItemLocalHeader header = new ZipItemLocalHeader();

    header.FileName = "File1.zip";
    writer.WriteItemLocalHeader( header );

    // Create a write stream that wraps the item's data
    using( Stream itemStream = writer.GetItemDataStream() )
    {
      // Feed the item stream to a new instance of ZipWriter
      using( ZipWriter nestedWriter = new ZipWriter( itemStream ) )
      {
        /* The 'using' statement will insure the nested zip file is properly terminated */

        // Add an item and some data into the nested zip file
        header.FileName = "File1.dat";
        nestedWriter.WriteItemLocalHeader( header );
        nestedWriter.WriteItemData( MediumFile1 );
      }
    }
  }
}

private void ReadZipArchive( Stream archiveStream )
{
  using( ZipReader reader = new ZipReader( archiveStream ) )
  {
    ZipItemLocalHeader header;

    while( ( header = reader.ReadItemLocalHeader() ) != null )
    {
      /* The component will not automatically identity what is and is
      * not a nested zip file. The application needs to have its own mechanism.
      *
      * This example will keep it simple and just look at the item's file name extension. */

      // If the item's extension is .zip
      if( StringComparer.OrdinalIgnoreCase.Compare( Path.GetExtension( header.FileName ), ".zip" ) == 0 )
      {
        // Create a read stream that wraps the item's data
        using( Stream itemStream = reader.GetItemDataStream() )
        {
          /* NOTE: While using a recursive call here makes for elegant and compact code that
          * helps illustrate the concept of nested zip archives, a maliciously crafted zip file
          * made up of a large number of nested zip files could make this code cause a stack overflow
          * due to excessive recursion. */

          // Call ourselves to read the nested archive
          this.ReadZipArchive( itemStream );
        }

        /* IMPORTANT: Before we can move on to the next item in the archive, ZipReader must have
        * reached the end of the current item's data. Reading a nested zip file does not ensure
        * this, so we need to make sure here by reading any remaining data into a dummy stream.
        *
        * Failure to do this will result in a ZipReaderException that reports that the object
        * is not in the correct state to read the next item header. */

        // Make sure we reach the end of the item's data
        reader.ReadItemData( Stream.Null );
      }
      else
      {
        // This example does not concern itself with normal items
        reader.ReadItemData( Stream.Null );
      }
    }
  }
}