Linq to SQL - Filter by "All Children" in "FilterCollection"

Question

I want to return all the entities of a database where ALL child elements of a parent are found in the control collection.

So, I thought something like this would work:

var toInclude = new List<int>{1, 2, 3};
var result = allObjs.Where(obj => obj.Children.All(child => toInclude.Contains(child)));

That doesn't work. It returns all entities where ANY ONE child is found in the control collection. I only want to return entities if ALL their children are found in the control collection.

I think I probably need to use a let statement, but my linq to sql is not journeyman level yet :).

Thanks for your insights.