Linq Query to Return Nested Arrays having specific Property Value

Question

I've been scouring multiple resources and can't figure this one out; I am trying to filter an Array of objects based on a Property that is nested a couple levels deep. I've simplified things, so let's say I have the following classes:

class A {
  B[] bb;
}

class B 
  C[] cc;
}

class C {
  string value;
}

And now the code:

A[] aa = ...;
A[] filteredAa = aa.Where(... //NEED HELP HERE

What I want to do is filter the aa array such that it gives me only those A elements that have at least one B element that have at least one C element has a value of "hello" (e.g. aa[0] would be included in the filteredAa array if aa[0].bb[3].cc[2].value = "hello").

Can this type of filtering even be done? I think and hope this makes sense, but please let me know if I can clarify any further.

whats the issue? no results? an error? only one result where there should be 20? — user1645826
– user1645826, Commented Jan 21, 2013 at 16:29
Sorry, I removed my code sample from my question because it actually wasn't working at all. Howie got it though! — Tony Rush
– Tony Rush, Commented Jan 21, 2013 at 16:43

Jon Skeet · Accepted Answer · 2013-01-21 16:30:30Z

4

You need to use Any - and it sounds like you need to use it twice:

var query = aa.Where(a => a.bb.Any(b => b.cc.Any(c => c.value == "hello")));

So working up from the inside:

A C object is useful if its value is "hello"
A B object is useful if any of its C values are useful
An A object is useful if any of its B values are useful
Where filters a sequence of A objects, leaving only the useful ones

You can use ToArray() at the end if you really want an array, but I would typically use ToList or just keep it as an IEnumerable<A>.

answered Jan 21, 2013 at 16:30

Jon Skeet

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7 Comments

Tony Rush Over a year ago

Great explanation, really puts the Any() method into context - didn't realize it was so easy.

SZT Over a year ago

how can I get value combined from A & C like ....Select(d => new {a.A, c.C})

Jon Skeet Over a year ago

@SZT: I'd need to know the exact details; it doesn't sound like it's really a very good fit for this question which is more about existence than projecting. I suggest you ask a new question with all the relevant details and a minimal reproducible example.

SZT Over a year ago

@JonSkeet could you take a look at this: stackoverflow.com/q/69828436/713847

Jon Skeet Over a year ago

@SZT: Given that you're using LINQ to SQL, the answer will depend on knowing what that supports; it's been years since I've used it I'm afraid.

|

cdhowie · Accepted Answer · 2013-01-21 16:29:40Z

1

Try this:

A[] filteredAa = aa.Where(a => a.bb.Any(b => b.cc.Any(c => c.value == "hello"))).ToArray();

answered Jan 21, 2013 at 16:29

cdhowie

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Comments

Servy · Accepted Answer · 2013-01-21 16:30:30Z

0

If you are looking for where Value is a specific value:

var result = aa.Where(a=>a.bb.Any(b => b.cc.Any(c => c.Value == "hello"));

If you just want to get all of those that have any value:

var result = aa.Where(a=>a.bb.Any(b => b.cc.Any(c => !string.IsNullOrEmpty(c.Value)));

answered Jan 21, 2013 at 16:30

Servy

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1 Comment

user1645826 Over a year ago

+1 i liked this because it used where its not null rather than hello, as his initial (unedited) question asked for results where value existed rather than where value was hello

Uchiha_Sasuke · Accepted Answer · 2013-01-21 16:39:46Z

0

filteredAa = aa.Where(x => x.bb.Any(y => y.cc.Any(z => z.value == "hello")))

answered Jan 21, 2013 at 16:39

Uchiha_Sasuke

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1 Comment

Uchiha_Sasuke Over a year ago

I am so sorry, It's too late, but next time, i'll do it;)

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