如何更新具有多个一对一关系的实体

Question

我有实体：DbDropPhoto、DbReferencePhoto 和 DbSimpleLine。 DbSimpleLines 由 bReferencePhoto 和 DbDropPhoto 使用。 我想使用每个 DbSimpleLine 的实体使 DbSimpleLine 只能链接到其中一个。 例如，如果 DbSimpleLine 是 DropPhotoHorizo​​ntalLine，则其他两个属性将为空。 我搜索了一些解决方案并找到了这个： http : //csharpwavenet.blogspot.com/2013/06/multiple-foreign-keys-with-same-table.html但现在我真的很困惑。 例如，根据示例，我的 DbSimpleLine 类应该有 ReferencePhoto 的集合，但实际上一个 DbSimpleLine 只能有一个 ReferencePhoto。 我在配置关系时做错了什么？ 对于关系配置，我使用 fluent API：

        modelBuilder.Entity<DbDropPhoto>()
            .HasOptional(b => b.SimpleHorizontalLine)
            .WithMany(a => a.DropPhotoHorizontalLine)
            .HasForeignKey(b => b.SimpleHorizontalLineId)
            .WillCascadeOnDelete(false);

        modelBuilder.Entity<DbDropPhoto>()
            .HasOptional(b => b.SimpleVerticalLine)
            .WithMany(a => a.DropPhotoVerticalLine)
            .HasForeignKey(b => b.SimpleVerticalLineId)
            .WillCascadeOnDelete(false);

        modelBuilder.Entity<DbReferencePhoto>()
            .HasOptional(b => b.SimpleReferencePhotoLine)
            .WithMany(a => a.ReferencePhoto)
            .HasForeignKey(b => b.SimpleReferencePhotoLineId)
            .WillCascadeOnDelete(false);

.WithMany() 让我很困惑，因为 SimpleVerticalLine（例如）不应该有很多 DropPhoto。

[Table("SimpleLines")]
public class DbSimpleLine
{
    [Key]
    public Guid SimpleLineId { get; set; }

    public ICollection<DbReferencePhoto> ReferencePhoto { get; set; }
    public ICollection<DbDropPhoto> DropPhotoHorizontalLine { get; set; }
    public ICollection<DbDropPhoto> DropPhotoVerticalLine { get; set; }
}

public class DbReferencePhoto
{
    [Key]
    public Guid ReferencePhotoId { get; set; }

    public Guid? SimpleReferencePhotoLineId { get; set; }
    public DbSimpleLine SimpleReferencePhotoLine { get; set; }
}

[Table("DropPhotos")]
public class DbDropPhoto
{
    [Key]
    public Guid DropPhotoId { get; set; }

    public Guid? SimpleHorizontalLineId { get; set; }
    public DbSimpleLine SimpleHorizontalLine { get; set; }

    public Guid? SimpleVerticalLineId { get; set; }
    public DbSimpleLine SimpleVerticalLine { get; set; }
}

此外，当我尝试将 dbDropPhoto 保存到数据库时，出现异常：

System.InvalidOperationException: '违反了多重性约束。 关系“DDrop.Db.DbDropPhoto_Drop”的角色“DbDropPhoto_Drop_Target”具有多重性1或0..1。

保存方法的代码：

public async Task UpdatDropPhoto(DbDropPhoto dropPhoto)
{
    using (var context = new DDropContext())
    {
        var dropPhotoToUpdate = await context.DropPhotos.FirstOrDefaultAsync(x => x.DropPhotoId == dropPhoto.DropPhotoId);

        try
        {                  
            if (dropPhoto.SimpleVerticalLine != null)
                context.SimpleLines.Add(dropPhoto.SimpleVerticalLine);
            if (dropPhoto.SimpleHorizontalLine != null)
                context.SimpleLines.Add(dropPhoto.SimpleHorizontalLine);
            context.Entry(dropPhotoToUpdate).CurrentValues.SetValues(dropPhoto);

            await context.SaveChangesAsync();
        }
        catch (Exception e)
        {
            throw new Exception(e.Message);
        }
        await context.SaveChangesAsync();
    }
}

Answer 1

最终这样做：

       modelBuilder.Entity<DbDropPhoto>()
            .HasOptional(c => c.SimpleHorizontalLine)
            .WithMany()
            .HasForeignKey(s => s.SimpleHorizontalLineId);

        modelBuilder.Entity<DbDropPhoto>()
            .HasOptional(c => c.SimpleVerticalLine)
            .WithMany()
            .HasForeignKey(s => s.SimpleVerticalLineId);

        modelBuilder.Entity<DbReferencePhoto>()
            .HasOptional(c => c.SimpleReferencePhotoLine)
            .WithMany()
            .HasForeignKey(s => s.SimpleReferencePhotoLineId);

[Table("SimpleLines")]
public class DbSimpleLine
{
    [Key]
    public Guid SimpleLineId { get; set; }
}

[Table("ReferencePhotos")]
public class DbReferencePhoto
{
    [Key]
    public Guid ReferencePhotoId { get; set; }     
    public Guid? SimpleReferencePhotoLineId { get; set; }
    [ForeignKey("SimpleReferencePhotoLineId")]
    public virtual DbSimpleLine SimpleReferencePhotoLine { get; set; }
}

[Table("DropPhotos")]
public class DbDropPhoto
{
    [Key]
    public Guid DropPhotoId { get; set; }
    public Guid? SimpleHorizontalLineId { get; set; }
    [ForeignKey("SimpleHorizontalLineId")]
    public virtual DbSimpleLine SimpleHorizontalLine { get; set; }
    public Guid? SimpleVerticalLineId { get; set; }
    [ForeignKey("SimpleVerticalLineId")]
    public virtual DbSimpleLine SimpleVerticalLine { get; set; }
}