MVC5 EF 实体显然正在保存，但检索时为空

我有一个Account包含列表的类Payments，其中包含一个列表Products那是Pending, Sold or Refunded.

当选择Products要付款，我可以将它们添加到Payment对象，然后将整个对象保存到Account.

但是，当我在Pay行动，Account.Payments一片空白。

这里是AddProduct action:

public ActionResult AddProduct(List<Product> products)
{
    //var acc = Account.FetchAccountFromIdentity(User.Identity.GetUserName());
    var username = User.Identity.GetUserName();
    var acc = db.Accounts.First(u => u.EmailAddress == username);
    var payment = new Payment();

    foreach (var product in products)
    {
        if (product.IsSelected)
        {
            var tempProduct = db.Products.Find(product.ProductID);
            payment.Products.Add(tempProduct);
            payment.PaymentStatus = enPaymentStatus.Pending;
            payment.Gross += tempProduct.Price;
            payment.Vat += tempProduct.Price * 0.2;
            payment.Net += payment.Gross - payment.Vat;
         }
    }
    payment.AccountID = acc;
    if (acc.Payments == null) acc.Payments = new List<Payment>();
    acc.Payments.Add(payment);
    db.SaveChanges();

    return RedirectToAction("Pay", "Products", new {id = acc.AccountID} );
}

acc.Payments此时已正确填充任何相关付款。

然后是Pay action:

    public ActionResult Pay(int? id)
    {
        var acc = db.Accounts.Find(id);
        var data = new AccountPaymentView
        {
            Account =  acc,
            Payment = acc.Payments.First(p => p.PaymentStatus == enPaymentStatus.Pending)
        };

        return View(data);
    }

acc.Payments现在为空！？

知道我一定做错了什么吗？

Edit现在帐户类别：

    public class Account
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int AccountID { get; set; }
        [Display(Name = "Title")]
        public string Salutation { get; set; }
        [Required]
        [Display(Name = "First Name")]
        public string FirstName { get; set; }
        [Required]
        [Display(Name = "Last Name")]
        public string LastName { get; set; }
        [Required]
        [DataType(DataType.Password)]
        [Display(Name = "Password")]
        public string Password { get; set; }
        [Required]
        [DataType(DataType.Password)]
        [Compare("Password", ErrorMessage = "Passwords do not match. Please try again.")]
        [Display(Name = "Confirm Password")]
        public string ConfirmPass { get; set; }
        [Required]
        [DataType(DataType.EmailAddress)]
        [Display(Name = "Email Address")]
        public string EmailAddress { get; set; }
        public virtual ICollection<Address> Addresses { get; set; }
        public virtual ICollection<Payment> Payments { get; set; }
        public DateTime CreatedOn { get; set; }
        public virtual  ICollection<DateTime> VistsList { get; set; }
        public bool IsDeleted { get; set; }
        public enAccountType AccountType { get; set; }
}

Edit 2这是 DBContext 上的 OnModelCreating 方法（删除了不相关的部分）。我是否遗漏了一些明显的东西？

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    base.OnModelCreating(modelBuilder);

    modelBuilder.Properties<DateTime>()
        .Configure(c => c.HasColumnType("datetime2"));

    modelBuilder.Entity<Account>().HasOptional(x => x.Addresses).WithMany();
    modelBuilder.Entity<Account>().HasOptional(x => x.Payments).WithMany();
    modelBuilder.Entity<Payment>().HasOptional(x => x.Products).WithMany();
    modelBuilder.Entity<Payment>().HasOptional(x => x.AccountID);
    modelBuilder.Entity<Payment>().HasKey(x => x.PaymentID);

}

编辑3 检查了 Account.FetchAccountFromIdentity() ，它确实打开了一个新的上下文。所以现在它已被删除，我现在在 AddProduct 方法中使用上下文（上面更新了代码）。

现在保存时出现以下错误！

An object of type 'System.Collections.Generic.List`1[[PPPv2.Models.Payment, PPPv2,
Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]' 
cannot be set or removed from the Value property of an EntityReference of type 'PPPv2.Models.Payment'.

我尝试在 OnModelCreating 方法中强制建立 PK 关系，但似乎没有帮助。

为了清楚起见，这里是 Payment 类：

public class Payment
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int PaymentID { get; set; }
    public virtual Account AccountID { get; set; }
    public virtual ICollection<Product> Products { get; set; }
    public double Gross { get; set; }
    public double Net { get; set; }
    public double Vat { get; set; }
    public string TransactionCode { get; set; }
    public enPaymentStatus PaymentStatus { get; set; }
    public bool IsDeleted { get; set; }
    public DateTime PaidOn { get; set; }

    public Payment()
    {
        Products = new List<Product>();
        Gross = 0.0;
        Net = 0.0;
        Vat = 0.0;
        IsDeleted = false;
        PaidOn = new DateTime(2000, 1, 1, 0, 0,0);
    }

}

编辑4 根据要求，以下是产品型号：

public class Product 
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int ProductID { get; set; }
    public string Name   { get; set; }
    public string Description { get; set; }
    [DataType(DataType.Currency)]
    [DisplayFormat(DataFormatString = "£{0:#,###0.00}")]
    public double Price { get; set; }
    [DataType(DataType.Currency)]
    [Display(Name = "Total Estimated Legal Cost")]
    [DisplayFormat(DataFormatString = "£{0:#,###0.00}")]
    public double EstimatedTotalLegalCost { get; set; }
    public virtual ICollection<Overview> Overviews { get; set; }
    public virtual ICollection<Process> Processes { get; set; }
    public DateTime CreatedOn { get; set; }
    public DateTime LastUpdated { get; set; }
    public bool IsSelected { get; set; }
    public bool IsDeleted { get; set; }
}

如果您查看实体框架生成的表，您会发现只有三个表。给定您的数据模型，应该有映射的联结表Account and Payment互相反对（同样适用Payment and Product，并且您可能需要对您拥有的其他集合执行相同的操作）。

您遇到的关于无法投射的异常List of Products到一个是因为你的数据模型表明Products是一个集合，但数据库表实际上将其存储为之间的外键（即单个实体）关系Payment and Product.

如果我更改中的代码OnModelCreating方法如下，你的AddProducts方法按预期工作。

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    base.OnModelCreating(modelBuilder);

    modelBuilder.Properties<DateTime>().Configure(c => c.HasColumnType("datetime2"));

    modelBuilder.Entity<Account>().HasMany(x => x.Addresses)
        .WithMany().Map(t => t.ToTable("AccountAddresses"));
    modelBuilder.Entity<Account>().HasMany(x => x.Payments)
        .WithMany().Map(t => t.ToTable("AccountPayments"));
    modelBuilder.Entity<Payment>().HasMany(x => x.Products)
        .WithMany().Map(t => t.ToTable("PaymentProducts"));
    modelBuilder.Entity<Payment>().HasOptional(x => x.AccountID);
    modelBuilder.Entity<Payment>().HasKey(x => x.PaymentID);
}

更改来自如下代码：

modelBuilder.Entity<Payment>().HasOptional(x => x.Products).WithMany();

To:

modelBuilder.Entity<Payment>().HasMany(x => x.Products).WithMany().Map(t => t.ToTable("PaymentProducts"));

这样做会指示实体框架创建允许Payment收藏Products.