Setting nullable int to default does not make it nul
<p>I have a nullable int. I want to set its value to <code>null</code> so I do the following:</p>

<pre><code>int? X;
X = 1;
X = default(int?);
</code></pre>

<p>It keeps the old value of <code>1</code> instead of setting <code>X</code> to <code>null</code>.</p>

<p>How do I fix this?</p>
