Include children and grandchildren when selecting from database

Question

I have the following models

public class Parent
{
    public int Id { get; set; }
    public string Name { get; set; }
    public virtual List<Child> Child { get; set; }
}

public class Child
{
    public int Id { get; set; }
    public string Name { get; set; }
    public virtual List<GrandChild> GrandChild { get; set; }
}

public class GrandChild
{
    public int Id { get; set; }
    public string Name { get; set; }
}

What Im trying to do now is select a list of parents from the database with the children and grandchildren.

Tried the following with no joy:

List<Parent> parent = new List<Parent>();
parent = db.parent.ToList();

Thomas Levesque · Accepted Answer · 2014-01-03T14:22:23.130

5

Use the Include method:

parent = db.parent.Include(parent => parent.Child.Select(child => child.GrandChild)).ToList();

For older versions of Entity Framework, you have to use a string instead of a lambda expression:

parent = db.parent.Include("Child.GrandChild").ToList();

Or you can use the custom Include extension method I blogged about here.

edited Jan 03 '14 at 14:22

answered Jan 03 '14 at 14:10

Thomas Levesque

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Get the following error Cannot convert lambda expression to type 'string' because it is not a delegate type – Ernie Jan 03 '14 at 14:14
@Ernie, you're probably using an older version of EF. See my updated answer. – Thomas Levesque Jan 03 '14 at 14:22
Been trying with lambda expressions for awhile and couldnt figure out why its not working. Thanks for the help. – Ernie Jan 03 '14 at 14:27
For EF Core, consider using the syntax from this answer http://stackoverflow.com/a/38741905/1047812 – Uriah Blatherwick Dec 14 '16 at 17:20
is the .Include syntax for Eager Loading a guarantee that EF will load the relationships? would be good to know the circumstances under which it will load vs when it may be merely a hint... I cannot find any doco stating either way. – joedotnot Jul 14 '18 at 00:31

score 0 · Answer 2 · answered Jan 03 '14 at 14:27

0

in Linq to Sql you should use DataLoadOptions

var dlo = new DataLoadOptions();

dlo.LoadWith<Parent>(p => p.Child );
dlo.LoadWith<Child>(c=> c.GrandChild );
db.LoadOptions = dlo;

List<Parent> parent = new List<Parent>();
parent = db.parent.ToList();

answered Jan 03 '14 at 14:27

Morten Anderson

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Include children and grandchildren when selecting from database

2 Answers2