Missing a using directive or an assembly reference for .ToList() : <p>I have this code in the class constructor.</p>

<pre><code>this._images = images.Split('#').ToList();
</code></pre>

<p>It has always worked, but now it gives this error:</p>

<blockquote>
  <p>Error CS1061  'string[]' does not contain a definition for 'ToList' and no extension method 'ToList' accepting a first argument of type 'string[]' could be found (are you missing a using directive or an assembly reference?).</p>
</blockquote>

<p>What can I do to make it work?</p>
