title: linq to sql query interceptor
body: <p>I'm looking at implementing some LINQ to SQL but am struggling to see how we woudl add in access control business rules such as customer a can only view their orders.
  In ado.net data services, query intercptors do exactly what I am after, and can see how to check on update / insert / delete, but is there an equivalent of this:</p>
  
  <pre><code>[QueryInterceptor("Orders")] 
  public IQueryable&lt;Orders&gt; OnQueryOrders(IQueryable&lt;Orders&gt; orderQuery) 
  { 
  
        return from o in orderQuery 
           where o.Customers.ContactName == HttpContext.Current.User.Identity.Name 
           select o; 
  } 
  </code></pre>
  
  <p>Or wil I need to control via accessors along the line of:
      GetOrdersByCustomer(string customerId)</p>