Convert LINQ to DataServiceQuery Difficulties

I have the following query running in LinqPad 4 but cannot convert it to a usable DataServiceQuery.

from a in ServiceAppointmentSet
join b in ContactSet on a.RegardingObjectId.Id equals b.ContactId
where a.RegardingObjectId.Equals("xxxxxxxx")
select new 
{
a.RegardingObjectId, 
b.new_PrimaryCode
}

I need to join these 2 entities to retrieve information and it's proven to be difficult.

Thanks