linq - 实体框架核心对象循环

Question

我有两个实体：

public class Asset
    {
        public int Id { get; set; }
        public string Name { get; set; }

        [ForeignKey("Type")]
        public short TypeId { get; set; }
        public AssetType Type { get; set; }
    }

public class AssetType
    {
        public short Id { get; set; }
        public string Name { get; set; }
        public ICollection<Asset> Assets { get; set; }
    }

还有我的 DbContext：

public class ApplicationDbContext : DbContext
    {
        public DbSet<Asset> Assets { get; set; }
        public DbSet<AssetAccess> AssetAccesses { get; set; }

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

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        { }

        protected override void OnModelCreating(ModelBuilder builder)
        {
            base.OnModelCreating(builder);

            builder.Entity<AssetType>().HasIndex(entity => entity.Name).IsUnique();
        }
    }

当我尝试Assets像这样从数据库中选择时：

var assets = _dbContext.Assets
    .Include(asset => asset.Type)
    .ToList();

我收到了Asset他们的列表，Types但在Type对象中有关联Asset对象的列表，因此它无休止地重复。

[
    {
        "id": 12,
        "name": "asset",
        "type": {
            "id": 1,
            "name": "type",
            "assets": [
                {
                    "id": 12,
                    "name": "asset",
                    "type": {
                        ... and so on ...
                    }
                },
                {
                    "id": 13,
                    "name": "asset",
                    "type": {
                        ... and so on ...
                    }
                }
            ]
        },
    },
    ...
]

我只想收到Asset内部列表，仅此而已Type。那么我怎样才能摆脱这种循环呢？在启动时，我定义了这个：

services.AddMvc()
    .SetCompatibilityVersion(CompatibilityVersion.Version_2_2)
    .AddJsonOptions(option => option.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore);

但它不起作用。

标签： linqasp.net-coreentity-framework-core

Answer 1

要返回 ViewModel 而不需要额外的循环对象，请尝试按照以下步骤操作：

1. 视图模型

   public class AssetVM
   {
       public int Id { get; set; }
       public string Name { get; set; }
       public AssetTypeVM Type { get; set; }
   }
   
   public class AssetTypeVM
   {
       public short Id { get; set; }
       public string Name { get; set; }
   }
   

2. 轮廓

   public class ModelProfile: Profile
   {
       public ModelProfile()
       {
           CreateMap<AssetType, AssetTypeVM>();
           CreateMap<Asset, AssetVM>();
       }
   }
   

3. 利用

   var assets = _context.Assets
               .Include(asset => asset.Type)
               .ToList();
   var assetsVM = _mapper.Map<List<AssetVM>>(assets);