silverlight - Passing computed values with RIA Services -

I am trying to find a way to get additional data with the organizations obtained from a RIA domain service. For example, suppose I want to display a datagrid for "order" and want to include a column for the total items in an order.

  order number | Customer Name | *No. Ordered items * 4545 | John | 4 1234 Mike | 7   
 On the server side, with a Linq query, I could:  
  var in queries = from institutions. Order New OrderWithItemCount Choose {Order = O, MadCount = o. ITEMS.COUNT ()};   
 ... and it will retrieve my commands together with all the items.  
 The problem is, I can not get it to broadcast anyway Silverlight client results through the domain service I think I can use a standard WCF service, but what does it enjoy? is?  
  Update   
  What happened because of the real problem ...   
 I at one point In fact, had already tried " Easy Way ", which Nissan Fan and Florian Lim had told. When I tried to do this, I was not getting all my data. (I need to include the customer  person  to get their names.) It has been found that there was a limit to RIA services that actually had a limit of EF 4.0, by saying that  entities.order. Included in this ("Customer")  will not work if you select a new type which is not  order . Your selection is clearly select  o.Customer  and EF will automatically wire the selected person to unassigned property on the  order .   
 
 
  Easy Way:   
 Just enter your order class Additional fields can be added in a partial classroom) and populate in your domain service.  
  Complex but more flexible way:   
 Define as a unit with the command (it requires a [key] attribute), then that Move.  
  Public category OrderWithItemCount {[Key] Public int id {get; Set; } // You need this, so that the domain specialists can return them together at the client. Public Entry (Received; Set; } [Include] [Association ("order-reference", "order-ed", "id")) Public order order {get; Set; } Public AT itemcount {receive; Set; } Public Interest Subscriber {Received; Set; }} Public IQueryable & lt; OrderWithItemCount & gt; GetOrdersWithItemCount () {var queries = from institutions Select new order for order itemcount {order id = o.id., order = o, mdcount = o.itimes.count, customer = o. Customers, // Make sure the EF includes customers }; Return query; }   
 There may be minor errors in the code because I can not test it at this time, but I have recently implemented something similar.