Filtering IQueryable sub list

Question

Working with Entity Framework, but that\'s probably irrelevant If I have an Iqueryable, how do I filter a sub list and keep it IQueryable so it doesn\'t yet hit the DB?

Answer 1

I think what you are looking is SelectMany. As an example for your case is something like this:

  positiveItems = items.SelectMany(x => x.SubItem).Where(x=> x.ID == 1).Select(x=>x.Item);
  //items still IQueryable , so we can concat it with another IQueryable

  negativeItems = items.SelectMany(x=>x.SubItem).Where(x=>x.ID != 1).Select(x=>x.Item);


  //just an using option
  allItems = positiveItems.Concat(negativeItems);

And just a suggestion. For high number of reference object set, you can use ValueInjecter It is very simple and fast. I used it couple of production projects and it saved my tons of times.