using (ArchiveFile archiveFile = new ArchiveFile(@"Archive.ARJ"))
{
    archiveFile.Extract("Output"); // extract all
}

using (ArchiveFile archiveFile = new ArchiveFile(@"Archive.ARJ"))
{
    foreach (Entry entry in archiveFile.Entries)
    {
        Console.WriteLine(entry.FileName);
        
        // extract to file
        entry.Extract(entry.FileName);
        
        // extract to stream
        MemoryStream memoryStream = new MemoryStream();
        entry.Extract(memoryStream);
    }
}

using (ArchiveFile archiveFile = new ArchiveFile(@"c:\random-archive"))
{
    archiveFile.Extract("Output"); 
}

WebRequest request = WebRequest.Create ("http://www.contoso.com/file.aspx?id=12345");
HttpWebResponse response = (HttpWebResponse)request.GetResponse();

using (ArchiveFile archiveFile = new ArchiveFile(response.GetResponseStream())
{
    archiveFile.Extract("Output"); 
}