I'm running an ASP.NET Core Web API project and I have this model class with a self-referencing association :
public class VehicleCategory
{
[Key]
public int Id { get; set; }
public string description { get; set; }
[ForeignKey("ParentVehicleCategoryId")]
public int? ParentVehicleCategoryId { get; set; }
[JsonIgnore]
public virtual VehicleCategory ParentVehicleCategory { get; set; }
public virtual IEnumerable<VehicleCategory> subVehicleCategories { get; set; }
}
I have configured everything in EF to retrieve get all data and added this config into the startup.cs file to prevent looping:
services.AddControllers().AddNewtonsoftJson(options =>
options.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore
);
The problem is that when I try to get all data from the database, I end up with this json result :
[
{
"id": 7,
"description": "description 1",
"parentVehicleCategoryId": null,
"subVehicleCategories": [
{
"id": 9,
"description": "description 2",
"parentVehicleCategoryId": 7,
"subVehicleCategories": null
},
{
"id": 10,
"description": "description 3",
"parentVehicleCategoryId": 7,
"subVehicleCategories": null
}
]
},
{
"id": 9,
"description": "description 2",
"parentVehicleCategoryId": 7,
"subVehicleCategories": null
},
{
"id": 10,
"description": "description 3",
"parentVehicleCategoryId": 7,
"subVehicleCategories": null
}
]
Is there a way I can only have this data with only the array representing the children:
[
{
"id": 7,
"description": "description 1",
"parentVehicleCategoryId": null,
"subVehicleCategories": [
{
"id": 9,
"description": "description 2",
"parentVehicleCategoryId": 7,
"subVehicleCategories": null
},
{
"id": 10,
"description": "description 3",
"parentVehicleCategoryId": 7,
"subVehicleCategories": null
}
]
},
]
To get data I'm using this code:
var test = _raceContext.VehicleCategories
.Include(x => x.subVehicleCategories)
.ToList();
If you want to include only top-level entities, and their children listed inside, you could use a Where clause to get only those where ParentVehicleCategory is null:
var test = _raceContext.VehicleCategories
.Where(vc => vc.ParentVehicleCategory == null)
.Include(x => x.subVehicleCategories)
.ToList();
This way, the top-level list is the "parent-less" entities, but the second-level entities will appear in your tree, because those entities are all children of some parent, and is included because of your call to the Include method. If you have only two levels of hierarchy, this method will work for you, but if a "child" entity can also be a "parent", you will need to do some extra work.