Question

假设我有一个国家/州/城市的对象图，如下所示：

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; }
}

是否有一种简单的方法可以查询List<Country>以获取所有城市？

Answer 1

countryList.SelectMany(c => c.States).SelectMany(s => s.Cities)怎么样？

或许这个？

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

Answer 2

不能简单！： - ）

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

LINQ查询以导航对象层次结构

2 个答案: