多对多不加载集合属性的实体

Question

我有一个包含玩家集合的实体名册。

public class Roster
{
    public Roster()
    {
        Players = new List<Player>();
    }

    public int RosterId { get; set; }

    [MaxLength(100)]
    [Required]
    public string RosterName { get; set; }

    public ICollection<Player> Players { get; set; }
}
public class Player
{
    public int PlayerId { get; set; }
    [MaxLength(100)]
    [Required]
    public string PlayerName { get; set; }
    public virtual ICollection<Roster> Rosters { get; set; }
}

我已经使用 fluent api 定义了关系

// many to many Roster - Players
modelBuilder.Entity<Roster>()
.HasMany(t => t.Players)
.WithMany(t=>t.Rosters)
.Map(m =>
{
    m.ToTable("RosterPlayers");
    m.MapLeftKey("RosterId");
    m.MapRightKey("PlayerId");
});

我可以像这样将一名球员保存到名单中

var roster = rosterRepository.GetById(rosterId);
var player = playerRepository.GetById(playerId);

roster.Players.Add(player);
rosterRepository.Update(roster);
...

但是，当我检索花名册时，没有加载球员收藏。我用所有正确的值验证了数据存在，并且以下 sql 确实产生了数据。

SELECT * from Rosters r 
INNER JOIN RosterPlayers rp on r.RosterId = rp.RosterId
INNER JOIN Players p ON p.PlayerId = rp.PlayerId

我错过了什么？

Answer 1

将 Players 属性设为虚拟，以便 EF 可以延迟加载集合。

public class Roster
{

    //...........

    public virtual ICollection<Player> Players { get; set; }
}

您也可以预先加载Players 集合。

var rosters = db.Rosters.Include(r => r.Players).ToList();