How to group by on 2 child entities and get total of both this child entities?

Question

I want to get total variants run for my Test Version 0 i.e Test Id=100

This is my table and records:

Test:

Answer 1

Update

Ok Learning, here it is a solution..

var tot_variants_for_test =
    (from v_name in 
       (from t_op in test 
        select new { v_name = t_op.TestOperation.Select(sv => sv.SubVariants.Variants.Name) }
       ).First().v_name 
     select v_name)
    .Union(
    (from v_name in 
      (from t_opdf in test 
       select new { v_name = t_opdf.TestOperationDifference.Select(sv => sv.SubVariants.Variants.Name) }
     ).First().v_name
     select v_name))
   .Count();