title: Linq: select property collection
body: <p>I have two classes:</p>
  
  <pre><code>public class Person
  {
     public int Id{get;set;}
     public string Name{get;set;}
     public List&lt;Order&gt; Orders{get;set;}
  }
  public class Order
  {
     public int Id{get;set;}
     public string Data{get;set;}
     public decimal Sum{get;set;}
  }
  </code></pre>
  
  <p>I use Nhibernate Linq. If I want to get total sum of orders filtering by Persan.Name I do this:</p>
  
  <pre><code>var result = (from person in personRepository.Query
               from order in person.Orders
               where person.Name.Contains("off")
               select order).Sum(order =&gt; order.Sum);
  </code></pre>
  
  <p>How can I do the same using fluent syntax?</p>