EF Core ICollection does not contain a definition for 'Include'

Question

I have a head and a details model with navigation properties between them. I'd like to get head records with details included. This works fine but the detail records I got doesn't contain all properties I need so I tried to add Include().

EF Core says ICollection<RequestDetail> does not contain a definition for 'Include'. I have already tried with List<> navigation types and Microsoft.EntityFrameworkCore and System.Linq are both in my usings.

My models:

public class RequestHead
{
    public string Id { get; set; }
    public DateTime CreateDate { get; set; }
    public int CreateUserId { get; set; }
    [ForeignKey("CreateUserId")]
    public User CreateUser { get; set; }

    public virtual ICollection<RequestDetail> Details { get; set; }
}
public class RequestDetail
{
    [Key]
    public int Id { get; set; }

    public string RequestHeadId { get; set; }        
    [ForeignKey("RequestHeadId")]
    public RequestHead RequestHead { get; set; }

    public DateTime CreateDate { get; set; }
    public int CreateUserId { get; set; }
    [ForeignKey("CreateUserId")]
    public User CreateUser { get; set; }
}

Select:

 var requests = (from r in _ctx.RequestHeads
                select new RequestDTO {
                    AcceptDate = r.AcceptDate,
                    AcceptUser = r.AcceptUser,
                    AcceptUserId = r.AcceptUserId,
                    Details = r.Details != null ? 
 r.Details.Include(x => x.BuyerUser).Select(x => new 
 RequestDetailDTO(x, x.Attachments.ToArray(), x.Product)).ToArray() : null});

Update#1:

This is not a Json.ReferenceLoopHandling problem. It is already ignored in startup.cs and my problem is that I can't use Include() even in my code not just not having the neccessary properties in the json.

Possible duplicate of [Entity Framework core .Include() issue](https://stackoverflow.com/questions/38550806/entity-framework-core-include-issue) — Afonso, Jul 24 '18 at 09:13
I think this is not duplicate. I already have Json.ReferenceLoopHandling.Ignore and my problem is that I can't even use Include() in my code not that it doesn't give me the neccessary properties. — Perrier, Jul 24 '18 at 09:21
it's like the error says. .Include is only available for IQueryables, while r.Details is an ICollection (a navigation property itself). Include x=>x.Details.Select(y=>y.BuyerUser) instead. — DevilSuichiro, Jul 24 '18 at 09:31
@DevilSuichiro Right, I just had to add the navigation properties to the select and it loaded them all. Thanks! Will you post an answer? — Perrier, Jul 24 '18 at 09:49

score 3 · Accepted Answer · answered Jul 24 '18 at 10:39

It's like the error suggests: Your property r.Details is an ICollection (a navigation property) and does not expose an .Include() method, which is only available for IQueryables (Extension method). The include path(s) should point from the returned IQueryable to the navigation properties you wish to include, in your case this should be something along the lines of

.Include(x=>x.Details.Select(y=>y.BuyerUser))

score 2 · Answer 2 · edited May 06 '19 at 21:34

2

If developing on .NET - make sure you are using the System.Data.Entity namespace.

using System.Data.Entity;

If on .NET Core - use Microsoft.EntityFrameworkCore instead.

using Microsoft.EntityFrameworkCore;

edited May 06 '19 at 21:34

eja

4,677
3
21
30

answered Jul 24 '18 at 09:22

Fábio Nascimento

2,644
1
21
27

2

There's no such namespace in .NET Core. It's equivalent is Microsoft.EntityFrameworkCore and it's already included. – Perrier Jul 24 '18 at 09:25
You are right @Perrier, this namespace is for .net, not for .net core. – Fábio Nascimento Dec 11 '18 at 14:54
1

That actually helped me with my problem, thanks! Easy thing to overlook. – icebat Aug 27 '21 at 09:56

EF Core ICollection does not contain a definition for 'Include'

2 Answers2