Passing HashSet<string> by reference
<p>Is it possible to pass a HashSet by reference to a function? This is my code currently.</p>

<p><strong>Main</strong></p>

<pre><code>this.scrapeFriends(startUsers, userIDs, 100);
</code></pre>

<p><strong>Function</strong></p>

<pre><code>private void scrapeFriends(StringCollection startUsers, ref HashSet&lt;string&gt; userIDs, int p)
{
    // Do something
}
</code></pre>

<p>If I remove the ref it works. If I add it, it don't and it won't compile.</p>
