.NET Core EF实体导航属性引发循环引用问题求助

我正在学习开发Web API，遇到了循环引用的问题：
用Scaffold-DbContext命令生成了TpVoStock和TpVoVehiclesAdvertisement两个实体类，想建立TpVoStock可选关联一个TpVoVehiclesAdvertisement的关系。添加导航属性后，执行包含Advertisement的查询时，返回结果出现循环引用——TpVoStock包含Advertisement，该Advertisement又包含原TpVoStock，循环往复。

我是.NET Core和EF的新手，试过调整导航属性写法、使用Fluent API等方法都无法解决，恳请帮忙！

相关代码 #

TpVoVehiclesAdvertisement实体 #

public partial class TpVoVehiclesAdvertisement
{
    [Key]
    public int Id { get; set; }

    [Column("stockId")]
    public int? StockId { get; set; }

    [StringLength(50)]
    [Unicode(false)]
    public string? Vin { get; set; }


    [ForeignKey("StockId")]
    public virtual TpVoStock Stock { get; set; }
}

TpVoStock实体 #

public partial class TpVoStock
{
    [Key]
    public int Id { get; set; }

    public int? StatusId { get; set; }

    public int DestCountryId { get; set; }


    public virtual TpVoVehiclesAdvertisement Advertisement { get; set; }
}

StockDbContext上下文 #

public partial class StockDbContext : DbContext
{
    public StockDbContext()
    {
    }

    public StockDbContext(DbContextOptions<StockDbContext> options)
        : base(options)
    {
    }

    public virtual DbSet<TpVoStock> TpVoStocks { get; set; }

    public virtual DbSet<TpVoVehiclesAdvertisement> TpVoVehiclesAdvertisements { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
//#warning To protect potentially sensitive information in your connection string, you should move it out of source code.
//You can avoid scaffolding the connection string by using the Name= syntax to read it from configuration - see https://go.microsoft.com/fwlink/?linkid=2131148.
//For more guidance on storing connection strings, see http://go.microsoft.com/fwlink/?LinkId=723263.
        => optionsBuilder.UseSqlServer("SomeConnectionString");

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.UseCollation("Czech_CI_AS");

        modelBuilder.Entity<TpVoStock>(entity =>
        {
            entity.ToTable("TP_VO_STOCK", tb =>
                {
                    tb.HasComment("VO Cars Stock");
                    tb.HasTrigger("TriggerLogChanges_TP_VO_STOCK");
                });

            entity.Property(e => e.StatusId).HasDefaultValueSql("((0))");
        });

        modelBuilder.Entity<TpVoVehiclesAdvertisement>(entity =>
        {
            entity.HasKey(e => e.Id).HasName("PK__TP_VO_VE__3214EC0752946F6B");
        });

        //modelBuilder.Entity<TpVoStock>()
        //    .HasOne<TpVoVehiclesAdvertisement>(s => s.Advertisement); have tried to do this one


        OnModelCreatingPartial(modelBuilder);
    }

    partial void OnModelCreatingPartial(ModelBuilder modelBuilder);
}

返回结果示例 #

//Stock
[{"id":10944,"statusId":2,"destCountryId":1,
//Advertisement
"advertisement":{"id":1,"stockId":10944,"vin":"VF3LCBHZHFS232605", 
//Again same TpVoStock
"stock":
{"id":10944,"statusId":2,"destCountryId":1,
//And Again same TpVoAdvertisement
"advertisement":{"id":1,"stockId":10944,"vin":"VF3LCBHZHFS232605"}]

循环引用的本质是实体间互相包含导航属性，JSON序列化时会触发无限递归，以下是几种实用解决方法：

1. 使用DTO（数据传输对象）【推荐】 #

不要直接返回EF实体，定义只包含业务所需字段的DTO类，从根源避免循环引用：

public class StockDto
{
    public int Id { get; set; }
    public int? StatusId { get; set; }
    public int DestCountryId { get; set; }
    public AdvertisementDto? Advertisement { get; set; }
}

public class AdvertisementDto
{
    public int Id { get; set; }
    public int? StockId { get; set; }
    public string? Vin { get; set; }
    // 此处不包含Stock导航属性，仅保留必要字段
}

查询时将实体映射为DTO返回：

var stocks = await _context.TpVoStocks
    .Include(s => s.Advertisement)
    .Select(s => new StockDto
    {
        Id = s.Id,
        StatusId = s.StatusId,
        DestCountryId = s.DestCountryId,
        Advertisement = s.Advertisement != null ? new AdvertisementDto
        {
            Id = s.Advertisement.Id,
            StockId = s.Advertisement.StockId,
            Vin = s.Advertisement.Vin
        } : null
    })
    .ToListAsync();
return Ok(stocks);

2. 配置JSON序列化忽略循环引用 #

在Program.cs中添加JSON序列化配置，让系统自动忽略循环引用：

builder.Services.AddControllers()
    .AddJsonOptions(options =>
    {
        options.JsonSerializerOptions.ReferenceHandler = ReferenceHandler.IgnoreCycles;
    });

3. 调整EF导航属性或关闭延迟加载 #

• 关闭延迟加载：在DbContext配置中禁用延迟加载代理：

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
    optionsBuilder.UseSqlServer("SomeConnectionString")
        .UseLazyLoadingProxies(false);
}

或者将实体中导航属性的virtual修饰符移除（EF默认对虚拟属性启用延迟加载）：

// 调整TpVoVehiclesAdvertisement
public TpVoStock? Stock { get; set; }
// 调整TpVoStock
public TpVoVehiclesAdvertisement? Advertisement { get; set; }

• 用Fluent API明确配置关系：在OnModelCreating中补充关系配置，确保EF正确识别关联：

modelBuilder.Entity<TpVoStock>()
    .HasOne(s => s.Advertisement)
    .WithOne(a => a.Stock)
    .HasForeignKey<TpVoVehiclesAdvertisement>(a => a.StockId)
    .IsRequired(false); // 对应StockId可空的可选关联

内容的提问来源于stack exchange，提问作者Kharitone