title: What's $-operator supposed to mean for a string?
body: <p>So, I've just had the following conversation with a user in <a href="https://stackoverflow.com/a/34558339/1525840">the comments section</a>.</p>
  
  <p>Me:  </p>
  
  <pre><code>Year year = new Year{ State = States.Happy };
  </code></pre>
  
  <p>Them:  </p>
  
  <pre><code>eventStream.ReceiveJoke += joke =&gt;  
      Console.WriteLine($"Pretty nice joke: {joke}, Thanks!!!");
  </code></pre>
  
  <p>And, nerdy as I am, I wonder what he meant by the dollar sign but I think it's too embarrassing to ask him.</p>