WebApi EF Core 2.1 Code First 设置导航属性,外键

Nuget:

Microsoft.AspNetCore.All

Microsoft.EntityFrameworkCore//Include 导航属性在此空间

Microsoft.EntityFrameworkCore.SqlServer

Microsoft.EntityFrameworkCore.Tools

微软懒加载文档:

https://docs.microsoft.com/en-us/ef/core/querying/related-data

注入EF:

        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();
            }
        }

种子数据:

  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);
        }

查询:

[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();
        }

实体:

 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>();
    }