EF Select Grandparent for Grandchildren - entity-framework

Question

Class Brands, Models, Generations, Modification
How to get all Brands for ModificationName == "ACK"
public class Brand
{
public Brand()
{
this.Models = new HashSet<Model>();
}
public int BrandId { get; set; }
public virtual ICollection<Model> Models { get; set; }
}
public class Model
{
public Model()
{
this.Generations = new HashSet<Generation>();
}
public virtual ICollection<Generation> Generations { get; set; }
public int? BrandId { get; set; }
public virtual Brand Brand { get; set; }
}
public class Generation
{
public Generation()
{
this.Modifications = new HashSet<Modification>();
}
public int GenerationId { get; set; }
public virtual ICollection<Modification> Modifications { get; set; }
public int? ModelId { get; set; }
public virtual Model Model { get; set; }
}
public class Modification
{
public int ModificationId { get; set; }
public string ModificationName { get; set; }
public int? GenerationId { get; set; }
public virtual Generation Generation { get; set; }
}

Answer 1

Another approach could be to use the Join operator. For example>
from currentBrand in Context.Brand
join currentModel in context.Model on currentBrand.Id equals currentModel.BrandId
join currentGeneration in context.Generations on currentGeneration.ModelId equals currentModel.id
join currentModeification in context.Modification on currentModeification.GenerationId equals currentGeneration .Id
Where currentModeification.ModificationName == "ACK"

Answer 2

Trick here is to use SelectMany method.
var query =
from b in ctx.Brands
where b.Models
.SelectMany(m => m.Generations.SelectMany(g => g.Modifications))
.Where(m => m.ModificationName == "ACK").Any()
select b;
UPDATE with includes
It will work only with EF Core 5
var query =
from b in ctx.Brands
.Include(b => b.Models)
.ThenInclude(g => g.Generations)
.ThenInclude(m => m.Modifications.Where(x => x.ModificationName == "ACK"))
where b.Models
.SelectMany(m => m.Generations.SelectMany(g => g.Modifications))
.Where(m => m.ModificationName == "ACK").Any()
select b;