title: Are double and double? interchangeable?
body: <p>Does anyone know whether a <code>double</code> is implicitly cast to <code>double?</code> (<code>Nullable</code> type)</p>
  <p>EDIT: What exactly is going on here?</p>
  <pre class="lang-cs prettyprint-override"><code>double d = 5;
  
  double? d2 = d as double?
  </code></pre>