title: C# callback from DLL
body: <p>I'm writing Application A and DLL B, both in C#.NET. How do I do the following:  </p>
  
  <ol>
  <li>A calls function in B  </li>
  <li>Want B to use delegate/callback to update status in UI of A  </li>
  </ol>
  
  <p>This is <em>not</em> about BackgroundWorker...that part works fine in A. What I can't see is how to let B know what function to call in A.</p>