Entity Framework Core 5.0.3 - One To One mapping with shadow property foreign keys - entity-framework-core

Question

For the life of me, I cannot get this to work properly. I have a relatively simple domain model that has a couple of navigation properties that I want to fill out via eager loading.
To keep my domain model pure, I have opted to use shadow properties as foreign keys, so they are not accessible by the client code.
This is the domain model:
public class CourseType : Entity
{
protected CourseType() { }
public CourseType(string name, CoachGroup coachGroup, bool active)
{
Name = name;
CoachGroup = coachGroup;
Active = active;
}
public string Name { get; private set; }
private int? _coachGroupId;
private int? CoachGroupId => _coachGroupId;
public virtual CoachGroup CoachGroup { get; private set; }
public int? AgeLimit { get; private set; }
public bool Active { get; private set; }
public bool ShowInSearchForm { get; private set; }
private List<Course> _accessGivingCourses = new List<Course>();
public virtual IReadOnlyList<Course> AccessGivingCourses => _accessGivingCourses?.ToList();
}
This is how I wire the configuration up:
public class CourseTypeConfiguration : IEntityTypeConfiguration<CourseType>
{
public void Configure(EntityTypeBuilder<CourseType> builder)
{
builder.ToTable("CourseTypes", "Courses");
builder.HasKey(p => p.Id);
builder.Property(p => p.Id).HasColumnName("CourseTypeId");
builder.Property(p => p.Name).HasColumnName("CourseTypeName");
builder.Property(p => p.Active).HasColumnName("IsActive");
builder.Property(p => p.ShowInSearchForm).HasColumnName("ShowInSearchForm");
builder.Property(p => p.AgeLimit).HasColumnName("AgeLimit");
builder.Property<int?>("CoachGroupId").HasField("_coachGroupId");
builder.HasOne(p => p.CoachGroup).WithOne().HasForeignKey<CourseType>("CoachGroupId").OnDelete(DeleteBehavior.Restrict);
builder.HasMany(p => p.AccessGivingCourses).WithMany("AccessGivingCourses")
.UsingEntity<Dictionary<string, object>>("CourseTypesAccessGivingCourses",
j => j.HasOne<Course>().WithMany().HasForeignKey("CourseId"),
j => j.HasOne<CourseType>().WithMany().HasForeignKey("CourseTypeId"),
j => j.ToTable("CourseTypesAccessGivingCourses")
);
builder.HasIndex("CoachGroupId").IsUnique(false);
}
}
This is how I extract the data via my repository class:
public override async Task<IEnumerable<CourseType>> GetAll()
{
try
{
return await Context.CourseTypes.Include(i => i.CoachGroup).Include(i => i.AccessGivingCourses).ToListAsync();
}
catch (Exception e)
{
Logger.LogCritical(e, $"Could not retrieve list of course type entities");
throw;
}
}
It ALMOST works, except for the fact that when I add or update entities, the CoachGroup link randomly gets lost for some updates. For others, it works just fine. It's like Entity Framework Core OR the database randomly loses track of it. Which is odd, because when I look in the database table, the foreign keys in the table are all there like they're supposed to!?
Does anyone have any idea what the hell I am doing wrong? Or if this is the correct approach to this problem at all? All I want to do is to load related data, but it's getting to the point where it's becoming rocket science to merely link a couple of optional relationships together...