Multiple joins using IQueryable in lightswitch

Question

I am using lightswitch and i have to join 3 tables in my query. Table A join Table B join table C where tableC.id == 10

partial void Query2_PreprocessQuery(int? dept, ref IQueryable query) {

    query = query.Join(Employee_Personal_Infoes, b => b.Employee_Personal_Info1.Emp_id, (b));

}

Answer 1

First off, if you add relationships between your tables, you shouldn't ever need to do manual joins. You would then just use the navigation properties that get created when you add the relationships.

Second, you can't change the shape of the entity in a query, or return a set of different entities. If your query is based say on a Customer entity, you can't return a query of CustomerAdresses, or a Client entity from that query. The query can only return a filtered set of the same entity that the query is based on.

Does that make sense?