linq question: querying nested collections

c# .net linq collections linq-to-xml
kitsune picture kitsune · Apr 6, 2009 · Viewed 50.1k times · Source

I have a Question class that has public List property that can contain several Answers.

I have a question repository which is responsible for reading the questions and its answers from an xml file.

So I have a collection of Questions (List) with each Question object having a collection of Answers and I'd like to query this collection of Questions for an Answer (ie by its Name) by using Linq. I don't know how to do this properly.

I could do it with a foreach but I'd like to know whether there is a pure Linq way since I'm learning it.

Answer

Daniel Brückner picture Daniel Brückner · Apr 6, 2009

To find an answer.

questions.SelectMany(q => q.Answers).Where(a => a.Name == "SomeName")

To find the question of an answer.

questions.Where(q => q.Answers.Any(a => a.Name == "SomeName"))

In fact you will get collections of answers or questions and you will have to use First(), FirstOrDefault(), Single(), or SingleOrDefault() depending on your needs to get one specific answer or question.

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