c# – 具有多对多未加载集合属性的实体

发布时间：2020-12-16 00:04:23 所属栏目：百科来源：网络整理

导读：我有一个实体名册,有一系列球员. public class Roster{ public Roster() { Players = new ListPlayer(); } public int RosterId { get; set; } [MaxLength(100)] [Required] public string RosterName { get; set; } public ICollectionPlayer Players { get

我有一个实体名册,有一系列球员.

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; }
}

我使用流畅的api定义了这种关系

// 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");
});

我可以将球员保存到这样的名单中

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

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

但是,当我检索名单时,不会加载球员集合.我验证了数据是否存在所有正确的值,以下sql确实提供了数据.

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？

解决方法

将Players属性设置为虚拟,以便EF可以延迟加载集合.

public class Roster
{

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

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

或者,您可以加载Players集合.

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

（编辑：李大同）

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