使用列表列表查询对象

Question

我想查询数据库并获取一个包含所有内部列表的运动对象，但由于某种原因我丢失了，选择仅在列表中深入 2 级，任何更深，并且列表属性的值为 @987654322 @, 结构示例

public class Sports
{
    public int id { get; set; }
    public string name { get; set; }
    public List<League> leagues { get; set; }
}
public class League
{
    public int id { get; set; }
    public string name { get; set; }
    public string description { get; set; }
    public List<Team> teams { get; set; }
}
public class Team
{
    public int id { get; set; }
    public string name { get; set; }
    public string successrate { get; set; }
    public List<Player> players { get; set; }
}
public class Player
{
    public int id { get; set; }
    public string name { get; set; }
    public int age { get; set; }
}

我在 MyAppContext 文件中创建了这个属性

public DbSet<Sports> sports { get; set; }

现在，当我使用 select 或 linq 或我尝试过的任何其他方式调用项目时，运动对象始终是 2 维的，这意味着它不会比嵌套列表中的两个级别更深！使用var sport=db.Sports.First() 的结果示例结果是{"id":1,"name":"Football","leagues":null} 或者如果我使用了 select()

   var sportQuery = db.sports.Select(
     s=>new Sports(){
        id=s.id,
        leagues=s.leagues,
        name=s.name
    }).First();

我仍然没有得到完整的信息{"id":1,"name":"Football","leagues":[{"id":1,"name":"fc","description":"Some Leauge","teams":null},{"id":2,"name":"al","description":"League","teams":null}]} 这是为什么！以及如何获得这样的完整对象

{"id":1,"name":"Football","leagues":[{"id":1,"name":"fc","description":"Some Leauge","teams":[{"id":1,"name":"real madrid","successrate":null,"players":[{"id":1,"name":"Cristiano Ronaldo","age":21},{"id":2,"name":"Iniesta","age":38}]},{"id":2,"name":"Barcelona","successrate":null,"players":[{"id":1,"name":"Cristiano Ronaldo","age":21},{"id":2,"name":"Iniesta","age":38}]}]},{"id":2,"name":"al","description":"League","teams":[{"id":1,"name":"real madrid","successrate":null,"players":[{"id":1,"name":"Cristiano Ronaldo","age":21},{"id":2,"name":"Iniesta","age":38}]},{"id":2,"name":"Barcelona","successrate":null,"players":[{"id":1,"name":"Cristiano Ronaldo","age":21},{"id":2,"name":"Iniesta","age":38}]}]}]}

我已经被困了好几天了，如果有任何帮助，将不胜感激

Answer 1

尝试以下：

namespace ConsoleApplication1
{
    class Program
    {

        static void Main(string[] args)
        {
            DataBase db = new DataBase();

            var sportQuery = db.sports.Select(s=> s.leagues.Select(l => l.teams.Select(t => t.players.Select(p => new {
                        playerid =  p.id,
                        playerName = p.name,
                        playerAge = p.age,
                        teamId = t.id,
                        teamName = t.name,
                        teamSucessrate = t.successrate,
                        leagueId= l.id,
                        leagueName= l.name,
                        leagueDescription = l.description,
                        sportId = s.id,
                        sportName = s.name
            }))
            .SelectMany(p => p))
            .SelectMany(t => t))
            .SelectMany(l => l)
            .ToList();
        }
    }
    public class DataBase
    {
        public List<Sports> sports { get; set;}
    }

    public class Sports
    {
        public int id { get; set; }
        public string name { get; set; }
        public List<League> leagues { get; set; }
    }
    public class League
    {
        public int id { get; set; }
        public string name { get; set; }
        public string description { get; set; }
        public List<Team> teams { get; set; }
    }
    public class Team
    {
        public int id { get; set; }
        public string name { get; set; }
        public string successrate { get; set; }
        public List<Player> players { get; set; }
    }
    public class Player
    {
        public int id { get; set; }
        public string name { get; set; }
        public int age { get; set; }
    }
}

Answer 2

使用Include() 和thenInclude() 解决的问题 https://docs.microsoft.com/en-us/ef/core/querying/related-data 但是，这并不能解释为什么Select() 只加载一个列表属性深，而且似乎我应该能够使用 select only 或 linq 加载对象