Question

I have a Question (q) with many Answers, each Answer has a variety of Texts, differing in language. I want to write a query to return all the answers in a given language (Lang) but I’m having difficulty figuring it out… here’s what I’m trying:

List<string> Answers = q.Answers
   .Select(x => x.Texts.Where(l => l.Language.ISO == Lang).Select(t => t.Value))
   .ToList();

which generates:

Cannot implicitly convert type 'System.Collections.Generic.List<System.Collections.Generic.IEnumerable<string>>' to 'System.Collections.Generic.List<string>'

maybe I can’t have a select inside a select… and:

List<string> Answers = q.Answers
   .Select(x => x.Texts.Where(l => l.Language.ISO == Lang))
   .Select(t => t.Value)
   .ToList();

where I would have thought the first select returns a Text, which means the second select can find its .Value… but, no:

'System.Collections.Generic.IEnumerable<Website.Models.Text>' does not contain a definition for 'Value' and no extension method 'Value' accepting a first argument of type 'System.Collections.Generic.IEnumerable<Website.Models.Text>' could be found (are you missing a using directive or an assembly reference?)

…perhaps I’m close but I can’t quite get it. how does one do this?

— Edit —

the credit here goes to SLaks. Here’s the final statement:

List<string> Answers = q.Answers
        .SelectMany(x => x.Texts)
        .Where(x => x.Language.ISO == Lang)
        .Select(x => x.Value)
        .ToList();

Answer 1

You need to call .SelectMany() to flatten the list of sets of Texts (IEnumerable<IEnumerable<string>>) into a single set of Texts (IEnumerable<string>).