选择里面的 Include in EF Core

Question

我有一个如下所示的实体（为简洁起见，部分删除，它包括许多其他属性）：

public class Tender
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }
    public string CreatorId { get; set; }
    [ForeignKey("CreatorId")]
    public virtual AppUser Creator { get; set; }
    public ICollection<TenderCircle> TenderCircles { get; set; } = new List<TenderCircle>();
}

该TenderCircles属性用于提供与另一个名为 的实体的多对多关系Circle。TenderCircle实体看起来像这样：

public class TenderCircle
{
    public int TenderId { get; set; }
    [ForeignKey("TenderId")]
    public Tender Tender { get; set; }
    public int CircleId { get; set; }
    [ForeignKey("CircleId")]
    public Circle Circle { get; set; }
}

现在，我正在执行以下查询（为了简洁起见，部分删除，通常它包含许多其他IncludeandThenInclude语句）：

return _context.Tenders
               .Include(t => t.Creator)
               .Include(t => t.TenderCircles.Select(tc => new { CirlceId = tc.CircleId, TenderId = tc.TenderId }))
               .ToList();

但是，它根本行不通。我想要实现的是，我只想从中获取TenderId和属性，而忽略实际的和对象。知道如何在EF Core中实现这一点吗？CircleIdTenderCircleTenderCircle

Answer 1

按如下方式编写您的查询：

return _context.Tenders.Select(t => new TenderViewModel
                       {
                          Id = t.Id,
                          Creator = t.Creator,
                          TenderCircles = t.TenderCircles.Select(tc => new TenderCircle { CirlceId =  tc.CircleId, TenderId = tc.TenderId }).ToList();
                       }).ToList();

然后TenderViewModel如下：

public class TenderViewModel
{
   public int Id { get; set; }
   public AppUser Creator { get; set; }
   public List<TenderCircle> TenderCircles { get; set; }
}