title: Can the C# interactive window interact with my code?
body: <p>In Visual Studio 2015 or later, I can open the 'C# interactive window', and run code:</p>
  
  <pre><code>&gt; 5 + 3
  8
  </code></pre>
  
  <p>That's cute. Now how can I interact <em>my code</em>—my classes? Assume I have a project open.</p>
  
  <pre><code>&gt; new Cog()
  (1,5): error CS0246: The type or namespace name 'Cog' could not be found (are you missing a using directive or an assembly reference?)
  </code></pre>