public void ConfigureServices(IServiceCollection services)

        {

            services.AddMvc();

            services.AddDbContext<AppDbContext>(options =>

            {

                //options.UseSqlServer(Configuration.GetConnectionString("SqlConnection"));

                options.UseSqlServer(Configuration["ConnectionStrings:SqlConnection"]);

            });

            services.AddMvc()

        .AddJsonOptions(

            options => options.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore

        );//设置禁止循环引用

            var serviceProvider = services.BuildServiceProvider();

            using (var context = serviceProvider.GetService<AppDbContext>())

            {

                context.Database.Migrate();

            }

        }

  protected override void OnModelCreating(ModelBuilder modelBuilder)

        {

            modelBuilder.Entity<Teacher>().HasMany(x=>x.Students);//设置关系

            modelBuilder.Entity<Teacher>().HasData(new List<Teacher>() {

                new Teacher() {  age=3, id=1, name="T1"}

                ,new Teacher() {  age=3, id=2, name="S2"}

               , new Teacher() {  age=3, id=3, name="F3"}

               , new Teacher() {  age=3, id=4, name="D4"}

            });

            modelBuilder.Entity<Student>().HasOne(c=>c.Teacher);//设置关系

            modelBuilder.Entity<Student>().HasData(new List<Student>() {

                new Student() {  age=3, id=1, name="T" ,TeacherId=2}

                ,new Student() {  age=3, id=2, name="S" ,TeacherId=2}

               , new Student() {  age=3, id=3, name="F" ,TeacherId=1}

               , new Student() {  age=3, id=4, name="D" ,TeacherId=3}

            });

            base.OnModelCreating(modelBuilder);

        }

[HttpGet]

        public IEnumerable<object> Get()

        {

            AppDbContext db = new AppDbContext();

            var student = db.Students.Include(x=>x.Teacher).Where(x=>x.id==1).ToList();

            var t = db.Teachers.Include(x => x.Students).Where(x=>x.id==2);

            return t.ToList();

        }

 public class Student

    {

        public int id { get; set; }

        public int age { get; set; }

        public string name { get; set; }

        [ForeignKey("Teacher.Id")]//设置外键,表.主键

        public int TeacherId { get; set; }

        //[JsonIgnore] 禁止序列化JSON

        public virtual Teacher Teacher { get; set; } //= new Teacher();

    }

    public class Teacher

    {

        public int id { get; set; }

        public int age { get; set; }

        public string name { get; set; }

        //[JsonIgnore] 禁止序列化JSON

        public virtual ICollection<Student> Students { get; set; }// = new List<Student>();

    }