Loading Related Data with Include()

[wangkanai]

I trying to get related data loaded with this api method

// GET: api/Department
[HttpGet]
public async Task<ActionResult<IEnumerable<Department>>> GetDepartment()
{
    var result = await _context.Departments
        .Include(d =>d.Children)
        .Where(d => d.Parent == null)                
        .ToListAsync();
    return result;
}

But i just end up with follow result Code 200

can't parse JSON.  Raw result:

[{"id":1,"parentId":null,"parent":null,"children":[{"id":2,"parentId":1

using the following model

public class Department
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    public int? ParentId { get; set; }
    public Department Parent { get; set; }
    public ICollection<Department> Children { get; set; }

    public int SiteId { get; set; }
    public Site Site { get; set; }

    public int DepartmentTypeId { get; set; }
    public DepartmentType DepartmentType { get; set; }
    [Required]
    public string Title { get; set; }
    public string Description { get; set; }
}

The full commit could be found here https://github.com/wangkanai/Organization/commit/683398c6e909cd3dc7049afc3ede66bfcf75c470
Its not that i never got this parent child relation working, i have a working model at https://github.com/wangkanai/EntityPattern/tree/master/ParentChild

Not sure what is going on, I run debug and found that data is getting load to var result.

Its like that IEnumerable<Department> is NOT parsing to ActionResult() or something.

Platform:

• ASP.NET Core 2.2
• EF Core 2.2

[smitpatel]

Did you configure your API to ignore loops?

[smitpatel]

Duplicate of aspnet/Mvc#4160

[wangkanai]

I will continue with this issue because I could not add more comments to aspnet/Mvc#4160

Well I have trying adding ReferenceLoopHandling.Ignore to Startup.cs

Look at this reference loop issue is still present.

But if add [JsonIgnore] the Api doesn't produce error, while children doesn't get loaded to the result.
This because the object is not get serialize to ActionResult.

Therefore, its seem like ASP.NET 2.2 & EFCore 2.2 doesn't respect this ReferenceLoopHandling.Ignore fix anymore.

Reference https://github.com/wangkanai/Organization/commit/9ca3b16752409cd153a33260cc39cbeb0c8e9149

[smitpatel]

@wangkanai - ReferenceLoopHandling is not something EF Core processes. It configures the Json serialization. EF just creates result on client side. Seems like you are having issues in your serialization code path rather than EF. Given ignoring loop in results works for people using serialization, try asking question on stackoverflow.