 <p>You cannot update a dll while it is in use, however you can.</p> <ul> <li>Make a copy of the dll with a new file name</li> <li>Load the copy of the dll into an app domain</li> <li>Talk to that app domain with .net remoting</li> <li>When the original dll changes repeat the above</li> </ul> <p>This is what Asp.net does under the covers. So another option is to use Aps.net to host your app.</p>