David Truxall

LINQ: Selecting in Nested Collections

This took me longer than it should have to figure it out, so I am documenting it for later reuse. The case here is described as such:

I have a collection of person objects, which themselves contain a collection of address objects. I want to find all the addresses in a given city:

public class Address

{

     public string Street { get; set; }

     public string City { get; set; }

     public string Region { get; set; }

     public string Postal { get; set; }

     public AddressType Location { get; set; }

}

public class Person

{

     public string Name { get; set; }

     public string ID { get; set; }

     public string Title { get; set; }

     public List<Address> Addresses { get; set; }

}

....

IEnumerable<Address> results = from guy in allPersons

                               from addressResult in guy.Addresses

                               where addressResult City == "London"

                               select addressResult;

I understand this is similar to a join in a SQL statement, but in my case the data does not come from a database but a service where I can't control data selection in that way.

Posted: Tuesday, June 23, 2009 3:07:00 AM (Eastern Standard Time, UTC-05:00)