title: Check if a variable is in an ad-hoc list of values
body: <p>Is there a shorter way of writing something like this:
  </p>
  
  <pre class="lang-cs prettyprint-override"><code>if(x==1 || x==2 || x==3) // do something
  </code></pre>
  
  <p>What I'm looking for is something like this:</p>
  
  <pre class="lang-cs prettyprint-override"><code>if(x.in((1,2,3)) // do something
  </code></pre>