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Start your free trialJon Andreas Grenness
5,055 PointsHow to use the Include operator to eagerly load the course's related teacher entity?
How do I eagerly load the courses's related teachers entity in this task properly? I've looked at similar questions, but none of the suggestions work for me. I must be doing something wrong...?
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
namespace Treehouse.CodeChallenges
{
public class Course
{
public Course()
{
Students = new List<CourseStudent>();
}
public int Id { get; set; }
public int TeacherId { get; set; }
[Required, StringLength(200)]
public string Title { get; set; }
public string Description { get; set; }
public int Length { get; set; }
public Teacher Teacher { get; set; }
public ICollection<CourseStudent> Students { get; set; }
}
}
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
namespace Treehouse.CodeChallenges
{
public static class Repository
{
public static List<Course> GetCourses()
{
using (var context = new Context())
{
return context.Courses
.OrderBy(c => c.Teacher.LastName)
.ThenBy(c => c.Teacher.FirstName)
.ToList();
}
}
public static List<Course> GetCoursesByTeacher(string lastName)
{
using (var context = new Context())
{
return context.Courses
.Where(c => c.Teacher.LastName == lastName)
.ToList();
}
}
public static Course GetCourse(int id)
{
using (var context = new Context())
{
return context.Courses
.Where(c => c.Id == id)
.Include(c => c.Teacher.Select(t => t.Teacher))
.SingleOrDefault();
}
}
}
}
2 Answers
Steven Parker
231,198 PointsHere's two hints:
- you don't need a Where because SingleOrDefault can apply the condition to filter the results
- you can simply reference the Teacher entity in the Include, you don' t need to select anything from it
Jon Andreas Grenness
5,055 PointsThat worked, thanks again!