实体框架中外键关系的空值

Question

I am creating a simple register module. I was able to successfully insert data via SQL Management studio but when tried to run the application, it is getting a null value ref. UserxId is 0 but the configuration is set to Identity and i'm not sure why AccessLevel is null. The code is very straightforward and unitofwork and generic repository is standard.

Property:

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; }


    }

Configuration:

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);

        }
    }

Below is the code for the controller

[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();
        }

The view is auto generated.

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

Basically I have two questions,

1. Why was the UserxId 0 when in fact it should be auto generated and auto incremented
2. Should the AccessLevel have value? I believe that property is used to map the foreign key.

Update: Property for AccessLevel:

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

Configuration:

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);
        }
    }

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: The UserxRepository was returning the null value ref. exception.

Before:

 private readonly UnitOfWork _unitOfWork;

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

After:

private readonly UnitOfWork _unitOfWork;

       public AuthController()
        {
            _unitOfWork = new UnitOfWork;
        }

What i was trying to accomplish on the before code was to create an abstraction by having UnitOfWork dependency class in the constructor so the object will be pre-instantiated.

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

Define Primary Key to Userx table on UserxId. It will automatically generate auto increment identity.

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; }
    }