Question

我是Code First的新手，所以请光临我。把头发拉了一整天试图让一个简单的过程正常工作后，我正在向社区寻求帮助。

以下是我的模型的源代码：

public class User
{
    public User()
    {
        GUID = Guid.NewGuid();
        Account = new Account();
        Location = new Location();
    }

    public long UserID { get; set; }
    public Guid GUID { get; set; }
    public string DisplayName { get; set; }
    public Location Location { get; set; }
    public virtual Account Account { get; set; }
}

public class UserConfiguration : EntityTypeConfiguration<User>
{
    public UserConfiguration()
    {
        HasKey(x => x.UserID);
    }
}

[ComplexType]
public class Location
{
    [MaxLength(2)]
    public string CountryCode { get; set; }
    [MaxLength(2)]
    public string StateCode { get; set; }
    public string City { get; set; }
}

public class Account
{
    public Account()
    {
        if (EmailAddresses == null) EmailAddresses = new Collection<EmailAddress>();
    }

    [ForeignKey("User")]
    public long AccountID { get; set; }

    public ICollection<EmailAddress> EmailAddresses { get; set; }

    public virtual User User { get; set; }
}

public class AccountConfiguration : EntityTypeConfiguration<Account>
{
    public AccountConfiguration()
    {
        HasKey(x => x.AccountID);
        HasMany(x => x.EmailAddresses).WithRequired(x => x.Account);
    }
}

public class EmailAddress
{
    [Key]
    public string Email { get; set; }

    public EmailTypes Type { get; set; }

    public long AccountID { get; set; }
    public virtual Account Account { get; set; }
}

public class EmailAddressConfiguration : EntityTypeConfiguration<EmailAddress>
{
    public EmailAddressConfiguration()
    {
        HasKey(x => x.Email);
        HasRequired(x => x.Account).WithMany(x => x.EmailAddresses).HasForeignKey(x => x.AccountID);
    }
}

这是我的实体类：

public class MyEntities : DbContext
{
    public MyEntities()
    {
        Database.SetInitializer<MyEntities>(new DropCreateDatabaseAlways<MyEntities>());
    }

    public DbSet<User> Users { get; set; }
    public DbSet<Account> Accounts { get; set; }
    public DbSet<EmailAddress> EmailAddresses { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Configurations.Add(new UserConfiguration());
        modelBuilder.Configurations.Add(new AccountConfiguration());
        modelBuilder.Configurations.Add(new EmailAddressConfiguration());

        base.OnModelCreating(modelBuilder);
    }
}

最后我的代码在测试控制台应用程序中运行：

static void Main(string[] args)
    {
        var id = CreateUser();

        using (MyEntities db = new MyEntities())
        {
            var a = db.Users.Find(id);
            var b = a.Account.EmailAddresses;
            var c = db.Accounts.Find(id);
            var d = db.EmailAddresses.Where(x => x.Account.AccountID == id).ToList();
        }

    }

    private static long CreateUser()
    {
        using (MyEntities db = new MyEntities())
        {
            var u = new User();
            u.DisplayName = "TEST";

            u.Location.CountryCode = "US";
            u.Location.StateCode = "HI";
            u.Location.City = "Kauai";

            EmailAddress e = new EmailAddress();
            e.Email = DateTime.UtcNow.Ticks + "@microsoft.com";
            e.Type = EmailTypes.Current;

            u.Account.EmailAddresses.Add(e);

            db.Users.Add(u);

            var cnt = db.SaveChanges();
            // Here I get a return of the 4 entities saved, and my model looks correct.

            return u.UserID;
        }
    }

保存模型后（CreateUser），我能够导航模型，一切看起来都很完美。

当我尝试将数据撤回时，问题出现了我的变数：

a - 导航到电子邮件地址显示0条记录。

b - 这也显示集合中的0条记录。

c - 导航到电子邮件地址会显示0条记录。

d - 在这里我可以获得电子邮件地址（但不能通过导航模型）

请帮忙！

Answer 1

访问导航属性的测试代码依赖于延迟加载。但是，您的Account.EmailAddresses集合未标记为virtual：

public ICollection<EmailAddress> EmailAddresses { get; set; }

导航属性必须为virtual（与您的User.Account属性一样）才能延迟加载。

作为旁注：我建议删除Account导航属性的实例化...

Account = new Account();

...来自User构造函数。这是一个众所周知的麻烦来源：

What would cause the Entity Framework to save an unloaded (but lazy loadable) reference over existing data?

EF 4.1 Code First: Why is EF not setting this navigation property?

实例化Location很好，因为它是复杂类型而不是导航属性。

保存后我的集合/模型看起来很好，但是在加载实体时我没有收到数据。我究竟做错了什么？

1 个答案: