WCF data services - Limiting related objects returned based on critera

I have an object graph consisting of a base employee object, and a set of related message objects.

I am able to return the employee objects based on search criteria on the employee properties (eg team) etc. However, if I expand on the messages, I get the full collection of messages back. I would like to be able to either take the top n messages (i.e. restrict to 10 most recent) or ideally use a date range on the message objects to limit how many are brought back.

So far I have not been able to figure out a way of doing this: I get an error if I attempt to filter on properties on the message (&$filter=employee/message/StartDate gives an error ">No property 'StartDate' exists in type 'System.Data.Objects.DataClasses.EntityCollection`1).

Attempting to use Top on the message related object doesn't work either.

I have also tried using a WebGet extension that takes a string list of employee IDs. That works until the list gets too long, and then fails due to the URL getting too long (it might be possible to setup a paging mechanism on this approach)...

Unfortunately the UI control I am using requires the data to be in a fairly specific hierarchical shape, so I can't easily come at this from starting on开发者_运维技巧 the message side and working backwards.

Outside of making multiple calls does anyone know of a method to accomplish this with wcf data services?

Thanks! M.

Looks like the only real way of doing this is in fact to reverse the direction of the query.

So instead of starting from the Employee, I go from the message side. You can filter back on the employee properties, and restrict on the Messages collection. Its not ideal, as it means iterating the collection on return to re-center it on the employee for what I am attempting to do, but it will work. The async nature of silverlight and rich client at least means while an extra iteration is required, it still appears to be reasonably fast.

Another interesting thing to note: the current version of odata/wcf data services does not support querying on properties of inherited classes, so I had to move the start/end date properties up to the base class in order to be able to restrict my search on them.

http://Site/Service.svc/Messages()?&$filter=Employee/OfficeName eq 'Toronto' and (year(StartDate) eq 2010 and month(StartDate) ge 9 )