How to Improve on this Entity Framework Query - sql-server

Question

I have the following entities:
Applicant : Person
PhoneNumber
PhoneType
The applicant is derived from Person. The Applicant has many PhoneNumbers (up to three). Each PhoneNumber has only 1 PhoneType.
public class Applicant : Person
{
public virtual ICollection<PhoneNumber> PhoneNumbers { get; set; }
}
public class PhoneNumber
{
public int PersonId { get; set; }
[Required]
[MaxLength(17)]
public string Number { get; set; }
public int PhoneTypeId { get; set; }
public virtual PhoneType PhoneType { get; set; }
}
public class PhoneType
{
[Required]
[MaxLength(24)]
public string Name { get; set; }
public virtual ICollection<PhoneNumber> PhoneNumbers { get; set; }
}
It seems to me that the two queries I am using could be merged and the foreach loop eliminated, but I already have a large number of joins in the first query and I am not sure how to merge them. The question is a two part question:
How could I merge the two queries and
If I don't merge the queries, how could I improve upon the PhoneNumber / PhoneType query.
The goal is to return an Applicant with a list of PhoneNumbers, and each PhoneNumber with a PhoneType. For clarity the types are : Home, Office and Mobile.
/*------------------------------------------*/
/* Obtain the Applicant */
/*------------------------------------------*/
IQueryable<Applicant> applicantQuery =
DbContext.Applicants.Where(a => a.CreatedBy == userId)
.Include(applicant => applicant.Address)
.Include(applicant => applicant.Address.StateProvince)
.Include(applicant => applicant.PhoneNumbers)
.Include(applicant => applicant.HomeChurch)
.Include(applicant => applicant.HomeChurch.Address)
.Include(applicant => applicant.HomeChurch.Address.StateProvince)
.Include(applicant => applicant.TripApplication);
Applicant applicant = applicantQuery.FirstOrDefault<Applicant>();
if (applicant != null && applicant.PhoneNumbers != null)
{
IQueryable<PhoneType> phoneTypeQuery = DbContext.Set<PhoneType>();
List<PhoneType> phoneTypes = phoneTypeQuery.ToList<PhoneType>();
foreach (PhoneNumber ph in applicant.PhoneNumbers)
{
ph.PhoneType = (phoneTypes.Where(pt => pt.Id == ph.PhoneTypeId)).First();
}
}
Thank you in advance for any help you might give.

Answer 1

EF Core supports loading multiple levels by combining Include() with ThenInclude(), more info here
To load the Phone along with PhoneTypes your query should look like this (I removed the rest of the relations for clarity):
var applicant = DbContext.Applicants.Where(a => a.CreatedBy == userId)
.Include(applicant => applicant.PhoneNumbers)
.ThenInclude(phone => phone.PhoneType)
.FirstOrDefault();