title: NPoco: Update some (but not all) columns using Expression notation
body: <p>Using NPoco, I'm trying to figure out how to update more than one column of an object (but not all of them).  This works...</p>
  
  <pre><code>db.Update(item, new[] { "status", "tracking_number", "updated_at" });
  </code></pre>
  
  <p>...but I'm trying to use the notation below so I can use my object's property names rather than the database column names.</p>
  
  <pre><code>int Update&lt;T&gt;(T poco, Expression&lt;Func&lt;T, object&gt;&gt; fields);
  </code></pre>
  
  <p>How do I list more than one column using the above syntax?  This will update a single column but I assume I can list more than one but I can't figure out the notation.</p>
  
  <pre><code>db.Update(item, i =&gt; i.Status);
  </code></pre>