Linq查询-列表中的另一个列表

Question

我试图在另一个(提供的)列表中选择具有至少一个城市名称的国家。不好意思，难以解释，请看下面的代码:

当我调用getlistofnations，它应该返回NZ和CN。我还想用Linq代替foreach。

    private static List<Country> Countries = new List<Country>(); 
    private static void Main()
    {
        var city1 = new City {Name = "Auckland"};
        var city2 = new City { Name = "Wellington" };
        var city3 = new City { Name = "Perth" };
        var city4 = new City { Name = "Sydney" };
        var city5 = new City { Name = "Beijing" };
        var country1 = new Country {Name = "NZ", Cities = new List<City> {city1, city2}};
        var country2 = new Country { Name = "AU", Cities = new List<City> { city3, city4 } };
        var country3 = new Country { Name = "CN", Cities = new List<City> { city5 } };
        Countries.Add(country1);
        Countries.Add(country2);
        Countries.Add(country3);
        List<String> cityNames = new List<string>{"Auckland", "Beijing"};
        var countries = GetListOfCountires(cityNames); // this should return NZ, and CN
    }
    public class Country
    {
        public string Name;
        public List<City> Cities = new List<City>();
    }
    public class City
    {
        public string Name;
    }
    public static List<Country> GetListOfCountires(List<String> cityNames)
    {
        List<Country> result = new List<Country>();
        foreach (var cityName in cityNames)
        {
            result.Add(Countries.Where(x=>x.Cities.Contains(cityName))); // error???
        }
        return result;
    }

谢谢

Answer 1

在您的城市名称列表和每个国家的城市列表之间执行交集，只返回存在交集的国家/地区。

var countries = Countries.Where(x => x.Cities.Intersect(cityNames).Any());

Answer 2

您需要做的是获得Any城市在cityNames列表中的国家

public static List<Country> GetListOfCountires(List<String> cityNames)
{
    return Countries
           .Where(country => country.Cities.Any(city => cityNames.Contains(city.Name))
           .ToList()
}