title: Where/what is the private variable in auto-implemented property?
body: <p>There is no (explicit)  reference to a firstName private variable which FirstName is supposed to be hiding. Could you explain how this works? 
  I assume there is some private variable that is being getted and setted.
  Thanks.</p>
  
  <pre><code>// auto-implemented property FirstName
  public string FirstName { get; set; }
  </code></pre>