C# 如何更新具有多个一对一关系的实体

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DropPhotoHorizontalLine，则其他两个属性将为null。我搜索了一些解决方案，找到了以下解决方案： 但现在我真的很困惑。例如，根据示例，我的DbSimpleLine类应该有ReferencePhoto集合，但实际上一个DbSimpleLine只能有一个ReferencePhoto。配置关系时我做错了什么？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);

---

结果是这样做的：

       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; }
}

modelBuilder.Entity（）
.has可选（c=>c.SimpleHorizontalLine）
.有很多
.HasForeignKey（s=>s.SimpleHorizontalLineId）；
modelBuilder.Entity（）
.HAS可选（c=>c.SimpleVerticalLine）
.有很多
.HasForeignKey（s=>s.simpleverticalineid）；
modelBuilder.Entity（）
.has可选（c=>c.SimpleReferencePhotoLine）
.有很多
.HasForeignKey（s=>s.SimpleReferencePhotoLineId）；
[表（“简单线”）]
公共类数据库
{
[关键]
公共Guid SimpleLineId{get；set；}
}
[表（“参考照片”）]
公共类DbReferencePhoto
{
[关键]
公共Guid ReferencePhotoId{get；set；}
公共Guid？SimpleReferencePhotoLineId{get；set；}
[外键（“SimpleReferencePhotoLineId”）]
公共虚拟DbSimpleLine SimpleReferencePhotoLine{get；set；}
}
[表格（“DropPhotos”）]
公共类照片
{
[关键]
公共Guid DropPhotoId{get；set；}
公共Guid？SimpleHorizontalLineId{get；set；}
[外键（“SimpleHorizontalLineId”）]
公共虚拟数据库impleline SimpleHorizontalLine{get；set；}
公共Guid？SimpleVerticalLineId{get；set；}
[ForeignKey（“SimpleVerticalLineId”）]
公共虚拟DbSimpleLine SimpleVerticalLine{get；set；}
}

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();
    }
}

       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; }
}