title: Is `??` thread safe in C#?
body: <p>Simple question:
  Are "<code>??</code>" and "<code>?.</code>" and "<code>? :</code>" thread-safe? And can I trust them? Or I should use other thread-safety solutions?
  For instance this code:</p>
  
  <pre><code>public static T Instance =&gt; _Instance ?? (_Instance = CreateInstance());
  </code></pre>
  
  <p>is thread-safe?</p>