C# 使用对象集合进行EF核心种子设定

我需要用种子数据填充数据库（SQL server）

对于“实习”表，我试图输入名为DesiredSkills的集合，但在运行迁移时，我收到以下错误消息：“对象引用未设置为对象的实例。”

是否可以使用列表之类的集合为数据库种子

DbContext：

public InternshipDbContext(DbContextOptions<InternshipDbContext> options) : base(options)
        {

        }
        public DbSet<Avatar> Avatars { get; set; }
        public DbSet<Company> Companies { get; set; }
        public DbSet<Internship> Internships { get; set; }
        public DbSet<Login> Logins { get; set; }
        public DbSet<Skill> Skills { get; set; }
        public DbSet<Trainee> Trainees { get; set; }
        public DbSet<TraineeRequest> TraineeRequests { get; set; }
        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.SharedTypeEntity<Dictionary<string, object>>("InternshipSkill");

            modelBuilder.Entity<Trainee>()
                .HasOne(x => x.Login)
                .WithMany()
                .OnDelete(DeleteBehavior.NoAction);

            modelBuilder.Entity<Internship>()
                .HasOne(x => x.Company)
                .WithMany()
                .OnDelete(DeleteBehavior.NoAction);

            modelBuilder.ApplyConfiguration(new LoginConfiguration());
            modelBuilder.ApplyConfiguration(new AvatarConfiguration());
            modelBuilder.ApplyConfiguration(new CompanyConfiguration());
            modelBuilder.ApplyConfiguration(new TraineeConfiguration());
            modelBuilder.ApplyConfiguration(new SkillConfiguration());
            modelBuilder.ApplyConfiguration(new InternshipConfiguration());
            modelBuilder.ApplyConfiguration(new TraineeRequestConfiguration());
        }

公共实习生DBContext（DbContextOptions）：基本（选项） { } 公共DbSet化身{get；set；} 公共数据库集公司{get；set；} 公共数据库集实习{get；set；} 公共数据库集登录{get；set；} 公共数据库集技能{get；set；} 公共数据库集{get；set；} 公共数据库集TrainerRequests{get；set；} 模型创建时受保护的覆盖无效（ModelBuilder ModelBuilder） { modelBuilder.SharedTypeEntity（“实习技能”）； modelBuilder.Entity（） .HasOne（x=>x.Login） .有很多 .OnDelete（DeleteBehavior.NoAction）； modelBuilder.Entity（） .HasOne（x=>x.Company） .有很多 .OnDelete（DeleteBehavior.NoAction）； ApplyConfiguration（新的LoginConfiguration（））； ApplyConfiguration（新的AvatarConfiguration（））； modelBuilder.ApplyConfiguration（新公司配置（））； modelBuilder.ApplyConfiguration（新的TraineConfiguration（））； ApplyConfiguration（新的SkillConfiguration（））； ApplyConfiguration（新的实习生配置（））； modelBuilder.ApplyConfiguration（新的TrainerRequestConfiguration（））； } 实习配置：

 public void Configure(EntityTypeBuilder<Internship> builder)
        {
            builder.HasData(
                new Internship { Id = 1, CompanyId = 1, CreationDate = DateTime.Now, Title = "Stage Software Developer", StartDate = DateTime.Now.AddDays(30), EndDate = DateTime.Now.AddDays(60), DesiredSkills = { new Skill { Id = 1, Name = "C#" }, new Skill { Id = 2, Name = "SQL" } }, FullTimeOrPartTime = InternshipType.Fulltime, IsRemote = RemoteExpectation.Whatever, PaymentExpectation = PaymentExpectation.Whatever, DescriptionFileUpload = uploadlink1, ShortDescription = "Wij zijn op zoek naar een schitterende Software Developer" },

                new Internship { Id = 2, CompanyId = 2, CreationDate = DateTime.Now, Title = "Stage Android Developer", StartDate = DateTime.Now.AddDays(32), EndDate = DateTime.Now.AddDays(62), DesiredSkills = { new Skill { Id = 1, Name = "C#" }, new Skill { Id = 10, Name = "Xamarin" } }, FullTimeOrPartTime = InternshipType.Fulltime, IsRemote = RemoteExpectation.Whatever, PaymentExpectation = PaymentExpectation.Whatever, DescriptionFileUpload = uploadlink2, ShortDescription = "Wij zijn op zoek naar een schitterende Android Developer" },

                new Internship { Id = 3, CompanyId = 3, CreationDate = DateTime.Now, Title = "Stage Angular Developer", StartDate = DateTime.Now.AddDays(35), EndDate = DateTime.Now.AddDays(65), DesiredSkills = { new Skill { Id = 1, Name = "C#" }, new Skill { Id = 4, Name = "Angular" } }, FullTimeOrPartTime = InternshipType.Fulltime, IsRemote = RemoteExpectation.Whatever, PaymentExpectation = PaymentExpectation.Whatever, DescriptionFileUpload = uploadlink3, ShortDescription = "Wij zijn op zoek naar een schitterende Angular Developer" },

                new Internship { Id = 4, CompanyId = 3, CreationDate = DateTime.Now, Title = "Stage Java Developer", StartDate = DateTime.Now.AddDays(35), EndDate = DateTime.Now.AddDays(65), DesiredSkills = { new Skill { Id = 7, Name = "Java" }, new Skill { Id = 2, Name = "SQL" } }, FullTimeOrPartTime = InternshipType.Fulltime, IsRemote = RemoteExpectation.Whatever, PaymentExpectation = PaymentExpectation.Whatever, DescriptionFileUpload = uploadlink4, ShortDescription = "Wij zijn op zoek naar een schitterende Java Developer" },

                new Internship { Id = 5, CompanyId = 4, CreationDate = DateTime.Now, Title = "Stage Software Developer", StartDate = DateTime.Now.AddDays(35), EndDate = DateTime.Now.AddDays(65), DesiredSkills = { new Skill { Id = 7, Name = "Java" }, new Skill { Id = 1, Name = "C#" } }, FullTimeOrPartTime = InternshipType.Fulltime, IsRemote = RemoteExpectation.Whatever, PaymentExpectation = PaymentExpectation.Whatever, DescriptionFileUpload = uploadlink5, ShortDescription = "Wij zijn op zoek naar een geniaal Sotftware Developer" },

                new Internship { Id = 6, CompanyId = 5, CreationDate = DateTime.Now, Title = "Stage Sotware Developer", StartDate = DateTime.Now.AddDays(35), EndDate = DateTime.Now.AddDays(65), DesiredSkills = { new Skill { Id = 12, Name = "C++" }, new Skill { Id = 1, Name = "C#" } }, FullTimeOrPartTime = InternshipType.Fulltime, IsRemote = RemoteExpectation.Whatever, PaymentExpectation = PaymentExpectation.Whatever, DescriptionFileUpload = uploadlink6, ShortDescription = "Wij zijn op zoek naar een bliljant Software Developer" }
                );
        }

public void配置（EntityTypeBuilder）
{
builder.HasData(
新实习{Id=1，CompanyId=1，CreationDate=DateTime.Now，Title=“Stage Software Developer”，StartDate=DateTime.Now.AddDays（30），EndDate=DateTime.Now.AddDays（60），DesiredSkills={new Skill{Id=1，Name=“C#”}，新技能{Id=2，Name=“SQL”}，FullTimeOrPartTime=internicshipType.Fulltime，IsRemote=remoteexpection.which，paymentexpection=paymentexpection.which，descriptionFileUploadLink1，ShortDescription=“Wij zijn op zoek naar een schitterende Software Developer”，
新实习{Id=2，CompanyId=2，CreationDate=DateTime.Now，Title=“Stage Android Developer”，StartDate=DateTime.Now.AddDays（32），EndDate=DateTime.Now.AddDays（62），DesiredSkills={new Skill{Id=1，Name=“C#”}，新技能{Id=10，Name=“Xamarin”}，FullTimeOrPartTime=internicshipType.Fulltime，IsRemote=remoteexpection.which，paymentexpection=paymentexpection.which，descriptionFileUploadLink2，ShortDescription=“Wij zijn op zoek naar een schitterende Android开发者”，
新实习{Id=3，CompanyId=3，CreationDate=DateTime.Now，Title=“Stage Angular Developer”，StartDate=DateTime.Now.AddDays（35），EndDate=DateTime.Now.AddDays（65），DesiredSkills={new Skill{Id=1，Name=“C#”}，新技能{Id=4，Name=“Angular”}，FullTimeOrPartTime=internishipType.Fulltime，IsRemote=remoteexpection.which，paymentexpection=paymentexpection.which，descriptionIleupload=uploadlink3，ShortDescription=“Wij zijn op zoek naar een schitterende Angular Developer”，
新实习{Id=4，CompanyId=3，CreationDate=DateTime.Now，Title=“Stage Java Developer”，StartDate=DateTime.Now.AddDays（35），EndDate=DateTime.Now.AddDays（65），DesiredSkills={new Skill{Id=7，Name=“Java”}，new Skill{Id=2，Name=“SQL”}，FullTimeOrPartTime=internicshipType.Fulltime，IsRemote=remoteexpection.which，paymentexpection=paymentexpection.which，descriptionFileUploadLink4，ShortDescription=“Wij zijn op zoek naar een schitterende Java Developer”，
新实习{Id=5，CompanyId=4，CreationDate=DateTime.Now，Title=“Stage Software Developer”，StartDate=DateTime.Now.AddDays（35），EndDate=DateTime.Now.AddDays（65），DesiredSkills={new Skill{Id=7，Name=“Java”}，new Skill{Id=1，Name=“C#“}，FullTimeOrPartTime=internishipType.Fulltime，IsRemote=remoteexpection.which，paymentexpection=paymentexpection.which，descriptionIleupload=uploadlink5，ShortDescription=“Wij zijn op zoek naar een geniaal software Developer”，
新实习{Id=6，CompanyId=5，CreationDate=DateTime.Now，Title=“Stage Sotware Developer”，StartDate=DateTime.Now.AddDays（35），EndDate=DateTime.Now.AddDays（65），DesiredSkills={new Skill{Id=12，Name=“C++”}，new Skill{Id=1，Name=“C#“}，FullTimeOrPartTime=internicshipType.Fulltime，IsRemote=remoteexpection.which，paymentexpection=paymentexpection.which，descriptionIleupload=uploadlink6，ShortDescription=“Wij zijn op zoek naar een bliljant Software Developer”}
);
}

DesiredSkills必须在他们自己的配置中播种。不能为嵌套对象设定种子。