实体框架代码优先 - 不能在 LINQ to 实体查询中构造实体或复杂类型

本文关键字：实体 查询 类型 复杂 to LINQ 代码 框架 不能 | 更新日期: 2023-09-27 18:33:30

第一个使用 EF 6 的项目。我有3张桌子，设施，Ewc和FacilityToEwc。每个设施可以有许多Ewc。

public class Facility
{
   public int FacilityId { get; set; }
   public string FacilityName {get; set;}
}
public class Ewc
{
   public int EwcId { get; set; }
   public sting EwcCode { get; set;}
}
public class FacilityToEwc
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int FacilityToEwcId { get; set; }
    public int FacilityId { get; set; }
    public Facility Facility { get; set; }
    public int EwcId { get; set; }
    public Ewc Ewc { get; set; }
}

希望这是正确的。问题是我需要一种方法来为每个设施返回 JSON 格式的所有 EWC 代码。这就是我所做的

public class FacilityDTO
 {
    public int FacilityId { get; set; }    
    public IEnumerable<Ewc> Ewc { get; set; }
}
public IEnumerable<FacilityDTO> GetFacilities()
{
   var result = (from currentFacility in db.Facilities
   select new FacilityDTO()
   {
      FacilityId = currentFacility.FacilityId,
      Ewc = from ewcDetail in db.FacilityToEwcs
      where ewcDetail.FacilityId == currentFacility.FacilityId
      select new Ewc { EwcCode = ewcDetail.Ewc.EwcCode }
   });
   return result;
}

当我执行上述方法时，我在此帖子标题中出现错误。感谢帮助。谢谢。

实体框架代码优先 - 不能在 LINQ to 实体查询中构造实体或复杂类型

我只需要创建 2 个表，一旦我将映射代码放置在 OnModelCreation 中，EF 就会自动创建映射表。请参阅下面的代码。

protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
            modelBuilder.Entity<Facility>()
            .HasMany(x => x.Ewc)
            .WithMany(x => x.Facility)
            .Map(x =>
            {
                x.ToTable("FacilityToEwc");
                x.MapLeftKey("FacilityId");
                x.MapRightKey("EwcId");
            });
            base.OnModelCreating(modelBuilder);
        }
public class Facility
{
   public int FacilityId { get; set; }
   public string FacilityName {get; set;} 
   public ICollection<Ewc> Ewc { get; set; }
}
public class Ewc
{
   public int EwcId { get; set; }
   public sting EwcCode { get; set;}
   public ICollection<Facility> Facility { get; set; }   
}
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