EF Core 实体循环参考

Question

我正在使用 C#.net 和 ef 核心。我有下面的模型。当我得到我的比赛列表时，我只想得到我的相关用户。但是，我得到了用户和所有用户的比赛。我怎样才能做到这一点？我必须执行以下操作才能显示我的比赛列表：

.AddJsonOptions(opt => opt.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore)

public partial class Competition
{
    public int CompetitionId { get; set; }
    public int UserId { get; set; }

    public User User { get; set; }
}

public partial class User
{

    public int UserId { get; set; }
    public string Email { get; set; }
    public string UserName { get; set; }

    public ICollection<Competition> Competitions { get; set; }
}

我有一个 API，它使用实体框架使用上述模型调用我的数据库。我的 api 中导致循环引用的调用如下：

    [Produces("application/json")]
    [Route("api/Competitions")]
    public class CompetitionsController : Controller
    {
        private readonly ApplicationDBContext _context;

        public CompetitionsController(ApplicationDBContext  context)
        {
            _context = context;
        }

        // GET: api/Competitions
        [HttpGet]
        public IEnumerable<Competition> GetCompetitions()
        {
            //return _context.Competitions;
            return _context.Competitions
                .Include(u => u.User).ToList();
        }
    }

下面是我在 ApplicationDBContext 类中创建模型的代码块：

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Competition>(entity =>
        {
            entity.HasKey(e => e.CompetitionId);

            entity.HasOne(d => d.User)
                .WithMany(p => p.Competitions)
                .HasForeignKey(d => d.UserId)
                .OnDelete(DeleteBehavior.ClientSetNull)
                .HasConstraintName("FK_Competitions_Users");
        });

        modelBuilder.Entity<User>(entity =>
        {
            entity.HasKey(e => e.UserId);

            entity.HasIndex(e => e.UserName)
                .HasName("UC_UserName")
                .IsUnique();

            entity.Property(e => e.Email)
                .HasMaxLength(40)
                .IsUnicode(false);

            entity.Property(e => e.UserName)
                .HasMaxLength(40)
                .IsUnicode(false);
        });
    }

Answer 1

老问题，但万一有人还在找。 一种解决方案是：

    services.AddMvc()
    .AddJsonOptions(options => {
        options.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
    });

Answer 2

您应该在构建时忽略了用户模型中的 Competitions 集合。

 modelBuilder.Entity<User>()
            .Ignore(b => b.Competitions);