WebAPI如何以JSON格式填充空结果

Question

我得到的结果是：

但是正如您所看到的，我的某些类返回空结果。这是我的代码：

MyDBContext：

 public partial class MyContext : DbContext
{
    public MyContext()
        : base("name=MyContext")

    {
       this.Configuration.ProxyCreationEnabled = false;
      //this.Configuration.LazyLoadingEnabled = false;
    }

    public virtual DbSet<Announcement> Announcement { get; set; }
    public virtual DbSet<Class> Class { get; set; }
    public virtual DbSet<Discontinuity> Discontinuity { get; set; }
    public virtual DbSet<Grade> Grade { get; set; }
    public virtual DbSet<Group> Group { get; set; }
    public virtual DbSet<Lesson> Lesson { get; set; }
    public virtual DbSet<Management> Management { get; set; }
    public virtual DbSet<Payment> Payment { get; set; }
    public virtual DbSet<Questions> Questions { get; set; }
    public virtual DbSet<Student> Student { get; set; }
    public virtual DbSet<Teacher> Teacher { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Class>()
            .HasMany(e => e.Student)
            .WithOptional(e => e.Class)
            .HasForeignKey(e => e.Class_Id);

        modelBuilder.Entity<Group>()
            .HasMany(e => e.Student)
            .WithOptional(e => e.Group)
            .HasForeignKey(e => e.Group_Id);

        modelBuilder.Entity<Lesson>()
            .HasMany(e => e.Teacher)
            .WithRequired(e => e.Lesson)
            .HasForeignKey(e => e.Lesson_Id)
            .WillCascadeOnDelete(false);

        modelBuilder.Entity<Student>()
            .HasMany(e => e.Discontinuity)
            .WithOptional(e => e.Student)
            .HasForeignKey(e => e.Student_Id);

        modelBuilder.Entity<Student>()
            .HasMany(e => e.Grade)
            .WithOptional(e => e.Student)
            .HasForeignKey(e => e.Student_Id);

        modelBuilder.Entity<Student>()
            .HasMany(e => e.Payment)
            .WithOptional(e => e.Student)
            .HasForeignKey(e => e.Student_Id);
    }
}

我的控制器类别：

public class StudentsController : ApiController
{
    private MyContext db = new MyContext();

    // GET: api/Students
    public IQueryable<Student> GetStudent()
    {
        return db.Student;
    }

    // GET: api/Students/5
    [ResponseType(typeof(Student))]
    public IHttpActionResult GetStudent(int id)
    {
        Student student = db.Student.Find(id);
        if (student == null)
        {
            return NotFound();
        }

        return Ok(student);
    }

    // PUT: api/Students/5
    [ResponseType(typeof(void))]
    public IHttpActionResult PutStudent(int id, Student student)
    {
        if (!ModelState.IsValid)
        {
            return BadRequest(ModelState);
        }

        if (id != student.Id)
        {
            return BadRequest();
        }

        db.Entry(student).State = EntityState.Modified;

        try
        {
            db.SaveChanges();
        }
        catch (DbUpdateConcurrencyException)
        {
            if (!StudentExists(id))
            {
                return NotFound();
            }
            else
            {
                throw;
            }
        }

        return StatusCode(HttpStatusCode.NoContent);
    }

    // POST: api/Students
    [ResponseType(typeof(Student))]
    public IHttpActionResult PostStudent(Student student)
    {
        if (!ModelState.IsValid)
        {
            return BadRequest(ModelState);
        }

        db.Student.Add(student);
        db.SaveChanges();

        return CreatedAtRoute("DefaultApi", new { id = student.Id }, student);
    }

    // DELETE: api/Students/5
    [ResponseType(typeof(Student))]
    public IHttpActionResult DeleteStudent(int id)
    {
        Student student = db.Student.Find(id);
        if (student == null)
        {
            return NotFound();
        }

        db.Student.Remove(student);
        db.SaveChanges();

        return Ok(student);
    }

    protected override void Dispose(bool disposing)
    {
        if (disposing)
        {
            db.Dispose();
        }
        base.Dispose(disposing);
    }

    private bool StudentExists(int id)
    {
        return db.Student.Count(e => e.Id == id) > 0;
    }
}

我该如何补习国外课程？我很好奇，有什么方法可以在结果开头输入类名。例如。如果我在学生中，则应以：“ Student”：[{“ Id”：18}]开始。我已经有了ModelBuilder。不，我真的不知道我在哪里做错了吗？

Answer 1

您需要.Include那些附加属性，这些属性将指示EF去为您检索数据。

为此，您需要将语法稍作更改：

var student = db.Student
    .Include(i => i.Discontinuity)
    .Include(i => i.Payment)
    .SingleOrDefault(s => s.Id == id);