LINQ query to navigate an object hierachy

Question

Let's say I have an object graph of Countries / States / Cities, like below:

public class City
{
    public string Name { get; set; }
}

public class State
{
    public List<City> Cities { get; set; }
}

public class Country
{
    public List<State> States { get; set; }
}

Is there a simple way to query a List<Country> to get all the cities?

Check out http://stackoverflow.com/questions/1590723/ ... the SelectMany() method will do it for you. — Matt Hamilton, Mar 18 '10 at 04:16
okay.. my q is a duplicate: http://stackoverflow.com/questions/1938409/linq-how-to-convert-the-nested-hierarchical-object-to-flatten-object I'm happy for this to be closed.. what's the protocol, do I just delete it? — TesterTurnedDeveloper, Mar 18 '10 at 04:19
That's not really a dup. The question you found is for a parent-child hierarchy which isn't quite the same as what you posed here. — Gabe, Mar 18 '10 at 04:40

score 3 · Accepted Answer · answered Mar 18 '10 at 04:18

3

How about countryList.SelectMany(c => c.States).SelectMany(s => s.Cities)?

Or maybe this?

var cities = from country in countryList
             from state in country.States
             from city in state.Cities
             select city;

answered Mar 18 '10 at 04:18

Gabe

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score 1 · Answer 2 · answered Mar 18 '10 at 04:20

1

Can't be simpler! :-)

var cities = from country in countries //List<Country>
             from state in country.States
             from city in state.Cities
             select city.Name;

answered Mar 18 '10 at 04:20

Enigmativity

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LINQ query to navigate an object hierachy

2 Answers2