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，但是由于某种原因，我丢失了，所以选择仅在列表中深入2个级别，任何更深的内容，并且lists属性的值为{{ 1}}，结构示例

null

我以此在MyAppContext文件中创建属性

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; }
}

现在，当我使用select或linq或其他尝试方式调用项目时，运动对象始终是2维的，这意味着它的深度不超过嵌套列表中的两个层次！使用public DbSet<Sports> sports { get; set; }的结果示例为var sport=db.Sports.First()或如果我使用select（）

{"id":1,"name":"Football","leagues":null}

我仍然没有获得完整的信息var sportQuery = db.sports.Select( s=>new Sports(){ id=s.id, leagues=s.leagues, name=s.name }).First(); 这是为什么！以及如何获得像这样的完整物体

{"id":1,"name":"Football","leagues":[{"id":1,"name":"fc","description":"Some Leauge","teams":null},{"id":2,"name":"al","description":"League","teams":null}]}

我已经被困了好几天，请给予任何帮助

Answer 1

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很深，而且看来我应该能够使用select only或linq加载对象

Answer 2

尝试以下操作：

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; }
    }
}

用列表列表查询对象

2 个答案: