Question

我正在创建一个简单的寄存器模块。我能够通过SQL Management Studio成功插入数据，但是当试图运行应用程序时，它获得了一个空值ref。 UserxId为0但配置设置为Identity，我不确定为什么AccessLevel为null。代码非常简单，单元工作和通用存储库是标准的。

属性：

public class Userx
    {
        public int UserxId { get; set; }
        public int Access_Level_ID { get; set; }
        public virtual AccessLevel AccessLevel { get; set; }
        public string username { get; set; }
        public string password { get; set; }


    }

配置：

public class UserxConfig : EntityTypeConfiguration<Userx>
    {
        public UserxConfig()
        {
            ToTable("Userx");
            HasKey(x => new { x.UserxId, x.Access_Level_ID });

            Property(x => x.UserxId)
                .HasColumnName("UserxId")
                .HasColumnType(SqlDbType.Int.ToString())
                .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);

            Property(x => x.Access_Level_ID)
             .HasColumnName("Access_Level_ID")
             .HasColumnType(SqlDbType.Int.ToString())
             .IsRequired();

            HasRequired(x => x.AccessLevel)
                .WithMany()
                .HasForeignKey(x => x.Access_Level_ID)
                .WillCascadeOnDelete(false);

        }
    }

以下是控制器的代码

[HttpPost]
        public ActionResult Registers(Userx userx)
        {

                if (ModelState.IsValid)
                {
                    using (var scope = new TransactionScope())
                    {
                        var encryptedPw = CustomEncrypt.Encrypt(userx.password);
                        var user = new Userx
                        {
                            Access_Level_ID = userx.Access_Level_ID,
                            username = userx.username,
                            password = userx.password
                        };
                        _unitOfWork.UserxRepository.Insert(user);
                        _unitOfWork.Save();
                        scope.Complete();
                    }
                }
                else
                {
                    ModelState.AddModelError("", "One or more fields have been");
                }

            return View();
        }

视图是自动生成的。

sample value while debugging, after the line, null value exception appears.

基本上我有两个问题，

为什么UserxId 0实际应该是自动生成并自动递增
AccessLevel应该有价值吗？我相信该属性用于映射外键。

更新： AccessLevel的属性：

public class AccessLevel
    {
        public int Access_Level_ID { get; set; }
        [Required]
        public string Level { get; set; }
        [Required]
        public string Description { get; set; }
    }

配置：

public class AccessLevelConfig : EntityTypeConfiguration<AccessLevel>
    {
        public AccessLevelConfig()
        {
            ToTable("AccessLevel");
            HasKey(x => x.Access_Level_ID);

            Property(x => x.Access_Level_ID)
                .HasColumnName("Access_Level_ID")
                .HasColumnType(SqlDbType.Int.ToString())
                .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
        }
    }

的DataContext：

public DbSet<AccessLevel> AccessLevel { get; set; }
        public DbSet<Userx> Userx { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Configurations.Add(new AccessLevelConfig());
            modelBuilder.Configurations.Add(new UserxConfig());
            base.OnModelCreating(modelBuilder);
        }

Null Value Reference Exception Screenshot

FIX： UserxRepository返回null值ref。异常。

在：

 private readonly UnitOfWork _unitOfWork;

       public AuthController(UnitOfWork unitOfWork;)
        {
            _unitOfWork = unitOfWork;
        }

后：

private readonly UnitOfWork _unitOfWork;

       public AuthController()
        {
            _unitOfWork = new UnitOfWork;
        }

我试图在之前的代码上完成的是通过在构造函数中使用 UnitOfWork 依赖类来创建抽象，因此该对象将被预先实例化。

Answer 1

public class Userx
    {
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)] //TELL EF TO AUTOGENERATE ID
        public int UserxId { get; set; }
        public int? Access_Level_ID { get; set; } //MAKE ACCESS_LEVEL_ID NULLABLE
        public virtual AccessLevel AccessLevel { get; set; }
        public string username { get; set; }
        public string password { get; set; }
    }

Answer 2

在UserxId上定义Userx表的主键。它会自动生成自动增量标识。

public class Userx
    {
        [Key] //TELL EF TO AUTOGENERATE ID
        public int UserxId { get; set; }
        public int? Access_Level_ID { get; set; } //MAKE ACCESS_LEVEL_ID NULLABLE
        public virtual AccessLevel AccessLevel { get; set; }
        public string username { get; set; }
        public string password { get; set; }
    }

实体框架中外键关系的空值

2 个答案: