Select multiple nested levels of child tables in Entity Framework Core

Question

I want to get multiple nested levels of child tables in Entity Framework Core using eager loading. I don't think lazy loading is implemented yet.

I found an answer for EF6.

var company = context.Companies
                 .Include(co => co.Employees.Select(emp => emp.Employee_Car))
                 .Include(co => co.Employees.Select(emp => emp.Employee_Country))
                 .FirstOrDefault(co => co.companyID == companyID);

My problem is that Select is not recognized in EF Core

Error CS1061 'Employees' does not contain a definition for 'Select' and no extension method 'Select' accepting a first argument of type 'Employees' could be found (are you missing a using directive or an assembly reference?)

My included namespaces:

using MyProject.Models;
using Microsoft.Data.Entity;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

What is the alternative for Select in EF Core.

devfric · Accepted Answer · 2015-12-02 15:15:43Z

133

You can use the keyword ThenInclude instead

e.g.

var company = context.Companies
             .Include(co => co.Employees).ThenInclude(emp => emp.Employee_Car)
             .Include(co => co.Employees).ThenInclude(emp => emp.Employee_Country)
             .FirstOrDefault(co => co.companyID == companyID);

answered Dec 2, 2015 at 15:15

devfric

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4 Comments

JasonX Over a year ago

Am I insane, or does this no longer work in EF Core 1.1.0? .ThenInclude treats the parent as an ICollection, offering me the collection properties instead of a single element's properties :/

Daniel Zolnai Over a year ago

@JasonX It is a bug in IntelliSense, just write you query as it would be an entity and it will work fine.

cdavid Over a year ago

@DanielZolnai did you report the bug by any chance - or how did you find it? Do you have a link to the GitHub issue?

ruffin Over a year ago

@cdavid It's listed here in the docs, and here on github. Unrelated: Painful that I have to do the .Include twice for grandchildren from the same child (in your (firste's) case, Employees). But excellent example; thanks.

Chris J · Accepted Answer · 2019-07-24 19:06:25Z

5

Also, the .ThenInclude intellisense for only works up to the 3rd level, for example:

_Context.A.Include(a => a.B).ThenInclude(B => B.C).ThenInclude(C => C.D)

The last part of that statement:

 .ThenInclude(C => C.D)

won't show "D", so you have to type D in yourself, then wait for a short period of time for the compilation error to disappear!

answered Jul 24, 2019 at 19:06

Chris J

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2 Comments

EGP Over a year ago

Using dotnet 5 and EF Core, intellisense is working at 3rd and 4th level (and possibly beyond).

Chris J Over a year ago

Nice. About time!

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