title: NHibernate - Add new property to class
body: <p>I'm a little confused about what goes on behind the scenes in NHibernate when I add a new property to a class.</p>
  
  <p>When I add a property 'Price' to an 'Item' class, my application throws an exception when retrieving Item objects because this new property isn't in the database:</p>
  
  <pre><code>[SqlException (0x80131904): Invalid column name 'Price'.]
  </code></pre>
  
  <p>Am I supposed to manually add a column to my DB table everytime I declare a new property in a class?</p>