Support for querying a hierarchy of self-referencing entities?

Hi,

Often you need to retrieve a whole hierarchy of self-referencing entities.

Consider this example:

public class Affiliate
{
  public int Id { get; set; }
  public string Name { get; set; }
  //The person who referred the current one
  public in ReferrerId { get; set; }
  [ForeignKey(nameof(ReferrerId)]
  public Affiliate Referrer { get; set; }
  //People the current has referred
  public virtual ICollection<Affiliate> Referred { get; set; } = new HashSet<Affiliate>();
}

Now I want to retrieve an Affiliate along with its children, grandchildren, and great grandchildren. Or I want to retrieve an Affiliate with its Referrer, he’s referrer’s referrer, and his referrer’s referrer’s referrer n levels up.

How can this be achieved in a single round-trip without involving stored-procedures?

• Can Linq Expressions be used for this?
• Is there a repo for that?
• Anything for EF6?

[mdczaplicki]

@alvaromongon this actually helped me, you just need to be careful not to create a loop in db. I have made these methods in my UnitOfWork:

public void LoadAllSubordinates(ref User user)
{
    this.LoadSubordinates(user);
}

private void LoadSubordinates(User user)
{
    this.context.Entry(user).Collection(u => u.DirectSubordinates).Load();
    foreach (var userDirectSubordinate in user.DirectSubordinates)
    {
        this.LoadSubordinates(userDirectSubordinate);
    }
}

[sophisma]

I know this thread is old but it pointed me in the right direction. I’m just posting this in case it helps other people. I had an issue where I had an hierarchy of categories of products, for instance, Storage->Internal Storage->SSD, and I had to retrieve the entire hierarchy from a child. The examples posted here were recursive, which can take a performance hit. You can do it iteratively this way:

        public Category GetById(int id)
        {
            var category = this.ObjectSet.FirstOrDefault(e => e.Id == id);

            this.IncludeParentCategories(category);

            return category;
        }

        private void IncludeParentCategories(Category category)
        {
            var currentCategory = category;

            do
            {
                this.UnitOfWork.Context.Entry(currentCategory).Reference(e => e.ParentCategory).Load();
                currentCategory = currentCategory.ParentCategory;
            }
            while (currentCategory != null);
        }