title: Interop type cannot be embedded
body: <p>I am creating a web application on the .NET 4.0 framework (beta2) in C#.</p>
  
  <p>When I try to use a assembly called "ActiveHomeScriptLib", I get the following error:</p>
  
  <blockquote>
    <p>Interop type
    'ActiveHomeScriptLib.ActiveHomeClass'
    cannot be embedded. Use the applicable
    interface instead.</p>
  </blockquote>
  
  <p>When I change the framework to version 3.5, I don't have any errors.</p>
  
  <p>What is an Interop Type and why does this only occur when I use the 4.0 framework?</p>