When using ria service for SL app, I can issue following async call to get a group of entity list.
LoadOperation<Person> ch =
this.AMSContext.Load(this.AMSContext.GetPersonQuery().Where(a => a.PersonID == this.performer.PersonID));
But I want to get some calculation, for example, sum(Commission), sum(Salary), the result is not entity, just a scalar value. How can I do this?