MVC中的多對多關係 - 使用外鍵寫入表格

Question

在模型中，我有3個表格與很多很多。

public class Order 
{ 
    [Key] 
    public int IdOrder { get; set; } 
    public string UserId { get; set; } 
    public virtual User User { get; set; } 
    public int IdOrderAttachment { get; set; } 
    public virtual OrderAttachment OrderAttachment { get; set; } 
    public virtual ICollection<Employee> Employee { get; set; } 

    [Required(ErrorMessage = "Specify the date of order acceptance")] 
    [Display(Name = "Date of acceptance of the order")] 
    [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)] 
    public DateTimeDateOfAcceptance { get; set; } 

    [Display(Name = "Date of completion planning")] 
    [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)] 
    public DateTime? DateOfCompletionPlanning { get; set; } 

    [Display(Name = "End Date")] 
    [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)] 
    public DateTime? EndDate { get; set; } 

    [Required(ErrorMessage = "Enter the subject")] 
    [MaxLength(200, ErrorMessage = "Name max 200 characters")] 
    [Display(Name = "Subject")] 
    public string Subject { get; set; } 

    public virtual ICollection<OrderPosition> OrderPosition{ get; set; } 
} 

public class OrderPosition 
{ 
    [Key] 
    public int IdOrderPosition { get; set; } 
    public int IdOrder { get; set; } 
    public int IdPosition { get; set; } 
    public virtual Order Order { get; set; } 
    public virtual Position Position { get; set; } 
} 

public class Position 
{ 
    [Key] 
    public int IdPosition { get; set; } 
    [Column(TypeName = "nvarchar(MAX)")] 
    [Display(Name = "Description")] 
    [UIHint("tinymce_jquery_full"), AllowHtml] 
    public string Description { get; set; } 
    public virtual ICollection<OrderPosition> OrderPosition { get; set; } 
} 


[HttpPost] 
[ValidateAntiForgeryToken] 
public ActionResult CreateOrder(HttpPostedFileBase file, DataOrderUserViewModel viewModel) 
{ 
    var userId = User.Identity.GetUserId();   

    if (ModelState.IsValid) 
    { 
     if (file != null && file.ContentLength > 0) 
     { 
      string path = "/Content/Layout/CompanyFile"; 
      if (!Directory.Exists(HttpContext.Server.MapPath(path))) 
      { 
       Directory.CreateDirectory(HttpContext.Server.MapPath(path)); 
      } 
      string filename = Path.GetFileName(file.FileName); 

      file.SaveAs(Path.Combine(HttpContext.Server.MapPath(path), filename)); 
      viewModel.NameFile = path+ "/" + filename; 

      //var nameFile = Path.GetFileName(file.FileName); 

      //var path = Path.Combine(Server.MapPath("/Content/Layout/CompanyFile"), nameFile); 

      //file.SaveAs(path); 

     } 

     var order = new Order() 
     { 
      DateTimeDateOfAcceptance = viewModel.DateTimeDateOfAcceptance, 
      Subject= viewModel.Subject,     
      UserId = userId 

     }; 

     var position = new Position() 
     { 
      Description = viewModel.Description 
     }; 

     var orderAttachment = new OrderAttachment() 
     { 
      NameFile= viewModel.NameFile, 
      Description = viewModel.Description2 
     }; 

     db.Order.Add(order); 
     db.Position.Add(position); 
     db.OrderAttachment.Add(orderAttachment); 
     db.SaveChanges(); 

    } 
    return RedirectToAction("Index", "Administration"); 
} 

我的問題是如何將數據寫入OrderPosition表。 我知道我應該先在Order and Position表中寫入數據。 然後，從這些數組中獲得兩個鍵，我應該讀取它們並將它們作爲外鍵保存，並將它們發送到OrderPosition。 這些說明的記錄應該是什麼樣的？

Answer 1

我需要在我的情況下定義以下關係嗎？

modelBuilder.Entity<OrderPosition>() 
     .HasKey(c => new { c.IdOrder , c.IdPosition }); 

    modelBuilder.Entity<Order>() 
     .HasMany(c => c.Subject) 
     .WithRequired() 
     .HasForeignKey(c => c.IdOrder); 

    modelBuilder.Entity<Position>() 
     .HasMany(c => c.Description) 
     .WithRequired() 
     .HasForeignKey(c => c.IdPosition);