entity-framework - 从linq到实体接收Dictionary ？

Question

问题How get array in linq to entity?的延续

但现在不是数组=>字典
城市类型为字典

 var sites = (from country in db.Countries
                        select new
                        {
                            Country = country.Title,
                            Cities = country.Cities.Select(m => m.Title)
                        })
                        .AsEnumerable()
                        .Select(country => new SitiesViewByUser()
                        {
                            Country = country.Country,
                            City = country.Cities.ToArray()
                        });

更新:

public class SitiesViewByUser
    {
        public string Country { get; set; }
        public Dictionary<int, string> City { get; set; }
    }

Answer 1

您可以使用ToDictionary从LINQ序列中创建字典。

第一部分是键，第二部分是值，例如

.Select(country => new SitiesViewByUser()
{
    Country = country.Country,
    City = country.Cities.ToDictionary(c => c, c => c);
});

假设 City上的 SitiesViewByUser定义为 Dictionary<string, string>
但是您的LINQ令人相当困惑。您正在创建一个匿名类型，假设其形状为 Country，但是上面具有 Country属性，该属性实际上是该国家/地区的 Title(国家名称？)。

您也仅收集了城市 Titles，因此我不确定要在 City类型的 SitiesViewByUser字典中使用什么值。

另外，什么是贴帖？ :\

更新

您可以执行以下操作:

var countries = (from country in db.Countries
   select new
   {
     Title = country.Title,
     CityIds = country.Cities.Select(c => c.Id),
     CityTitles = country.Cities.Select(c => c.Title)
   }).AsEnumerable();

// You have a collection of anonymous types at this point, 
// each type representing a country
// You could use a foreach loop to generate a collection 
// of SitiesViewByUser, or you could use LINQ:

var sitiesViewByUsers = countries.Select(c => new SitiesViewByUser
   {
      Country = c.Title,
      City = c.CityIds.Zip(c.CityTitles, (k, v) => new { Key = k, Value = v })
               .ToDictionary(x => x.Key, x => x.Value)
   };

另外，为什么不将 SitiesViewByUser类型更改为:

public class SitiesViewByUser
{
    public string Country { get; set; }
    public IEnumerable<City> Cities { get; set; }
}

然后，您可以做(使用流利的语法):

var sitiesViewByUsers = db.Countries.Select(c => new SitiesViewByUser
  {
    Country = c.Title,
    Cities = c.Cities
  });