Linq to Select Parent Objects Where Child Objects Have a Matching Child Object

Question

How would I go about writing a LINQ statement that selects the parent objects that have a matching child object in it's collection? Here's example classes.

class Parent {
    int ID { get; set; }
    string Name { get; set; }
    List<Child> Children { get; set; }
}

class Child {
    int ID { get; set; }
    string Name { get; set; }
    string Nickname { get; set; }
}

In the example above, I would like to return all of the parents that contain a child with a specific nickname.

Voting the question down was pretty harsh. I searched SO *and* Google both before typing out this abstract answer. If the tools here were better, maybe I wouldn't have a duplicate question. — Will Strohl, Mar 25 '15 at 01:44
Upvoted. This was the top result for my google search "linq select parent objects based on child objects". If I had the rep, I would unmark this as a duplicate; the linked question provides a similar answer, but the way the question title is phrased is not intuitively similar. — Will, Feb 04 '16 at 23:57
Many people on SO are way too quick to perform actions, without thinking them through. It's quite annoying and sometimes downright upsetting. — Will Strohl, Feb 05 '16 at 16:54

score 44 · Accepted Answer · answered Mar 24 '15 at 21:16

This is straightfoward Linq-to-Objects:

listOfParents.Where(p => p.Children.Contains(childObjectToMatch))

For Linq-to-Entities, if the child object isn't tracked as an entity you might need to match on the child object identifier field:

int childObjectIdToMatch = childObjectToMatch.ID;
dbContext.Parents.Where(p => p.Children.Any(c => c.ID == childObjectIdToMatch));

Linq to Select Parent Objects Where Child Objects Have a Matching Child Object

1 Answers1

Linked