title: Calling AddDays on a Nullable DateTime object
body: <p>I had used <code>AddDays(x)</code> method before on <code>DateTime</code> objects and it was working fine but now my object is defined like this:</p>
  
  <pre><code>public DateTime? To_Date { get; set; }
  </code></pre>
  
  <p>And looks like this one does not have a <code>AddDays</code> method.  How can I call it then? </p>