title: What does mean "?" after variable in C#?
body: <p>What does this condition mean?</p>
  
  <pre><code>if (!helper?.Settings.HasConfig ?? false)
  </code></pre>
  
  <p>P.S.</p>
  
  <ul>
  <li><code>helper</code> is variable of some <code>class</code></li>
  <li><code>Settings</code> is some <em>field</em></li>
  <li><code>HasConfig</code> is <em>field</em> too</li>
  </ul>