Return Only Child Entity Linq Entity Framework

Question

Given something like:

public class Parent
{
    public int Id { get; set; }
    public List<Child> Children { get; set; }
}

// There is no reference to the parent in the object model
public class Child
{
    public int Id { get; set; }
    public string MyProperty { get; set; }
}

is it possible to load only a child matching a particular condition, for a given Parent ID, without also loading the parent entity?

I have seen solutions that use projection to load the parent and zero or more children matching a condition.

How does your data model work if a child has no idea what it's parent is? — Alastair Pitts, Feb 26 '13 at 05:04
why not `db.Childs.Where(c => c.MyProperty == "something")`? — cuongle, Feb 26 '13 at 05:06
@AlastairPitts: The data model knows, but the object model does not. EF creates a column to represent the relationship in the child table, but does not expose it to the object model unless the parent object is expressly included as a property of the child object. — Eric J., Feb 26 '13 at 05:25
@EricJ. Ah. That makes sense, also makes it hard. Any specific reason the parent is not included as a property of the child? — Alastair Pitts, Feb 26 '13 at 05:34

score 5 · Accepted Answer · answered Feb 26 '13 at 05:12

If I understand you correctly, this should do it; it puts the conditions you want on both the parent and child, but selects only the child.

from parent in db.Parents
from child in parent.Children
where parent.Id = 4711 &&
      child.MyProperty == "olle"
select child;

Return Only Child Entity Linq Entity Framework

1 Answers1