Entity Framework Core loading self referencing results recursively - entity-framework-core

Question

I have a table like that,
public class Asset
{
public int id_asset { get; set; }
public int id_user { get; set; }
public int id_parent_asset { get; set; }
public string name { get; set; }
public virtual Asset Parent_Asset { get; set; }
public virtual ICollection<Asset> Child_Assets { get; set; }
public virtual User User { get; set; }
}
I want to get all children assets of an asset. I tried following code,
context.Asset.Where(o => o.name.Contains("Root")).Include(o => o.Child_Assets ).FirstOrDefault();
But it just contains one level children. I need to get all levels. I don't know that how many levels I should get so I need a recursive method or maybe there is already a method that is doing that.
Is there anyone who knows how can I handle this issue.

Answer 1

I had the same problem and was able to solve it using Lazy Loading instead of Eager loading. That may or may not be suitable for you.
With Lazy Loading you don't need to specify which navigation properties to load when you query the database (No need for the .Include calls). EF Core will automagically load in the related entities for you as you access them. ie get the root asset from the context and it's children will be there.
To use lazy loading you need to add Microsoft.EntityFrameworkCore.Proxies nuget package and then call .UseLazyLoadingProxies() when you configure the context. See the Docs for details https://learn.microsoft.com/en-us/ef/core/querying/related-data#lazy-loading
Also note that for the magic to happen the context that loaded the entity needs to know about the related entities (the child assets in your case). It won't go query the database for the child assets but if it has them in memory it will link them up. So in your case you will need to load all the assets then get the root asset and its children and their children will be there.
If you are using multiple contexts you can run into issues. Say the assets are loaded into one context and the users into another context, in that case root.User will be null because the context used to load the root asset doesn't have the users in memory.