title: NHibernate linq provider datediff
body: <p>Is where a way to write something like this:</p>
  
  <pre><code>public class Item
  {
      public DateTime Start { get; set; }
      public DateTime Finish{ get; set; }
  }
  
  Sessin.Query&lt;Item&gt;.Where( x =&gt; x.Start.AddHours( 3 ) &gt; x.Finish );
  </code></pre>
  
  <p>Now i get an exception </p>
  
  <blockquote>
    <p>[NotSupportedException: System.DateTime AddHours(Double)]</p>
  </blockquote>