title: How to force single inheritance?
body: <p>I have two classes:</p>
  
  <pre><code>public class A
  {
  }
  
  public sealed class B : A
  {
  }
  </code></pre>
  
  <p>And I want that only my <code>B</code> class (defined in the same assembly of <code>A</code>) can inherits <code>A</code>.<br>
  How can I do?</p>