Entity framework 4 Id'；首先使用EntityFramework代码时，不会进行更新

在前面的一个问题之后，我仍然首先在努力学习EF代码

我有3个表（在本例中，实际上还有更多），其中1个表使用多个Id来访问其他表

我有两个问题

1:保存到数据库时未设置装运和交付的Id（保留为“0”）。 2：使用DBMigrations时，会为RecordId创建两次索引

.Index(t => t.RecordId),
.Index(t => t.RecordId);

代码示例：

记录类别：

public class Record
{
    public Record()
    {
        Shipping = new Shipping();
        Delivery = new Delivery();
    }

    public int RecordId { get; set; }
    public int ShippingId { get; set; }
    public int DeliveryId { get; set; }

    public virtual Shipping Shipping { get; set; }
    public virtual Delivery Delivery { get; set; }
}

装运类别：

public class Shipping
{
    public int ShippingId { get; set; }
    public string ShippingName { get; set; }

    public virtual Record Record { get; set; }
}

交货类别：

public class Delivery
{
    public int DeliveryId { get; set; }
    public String DeliveryText { get; set; }

    public virtual Record Record { get; set; }
}

背景：

public class Context : DbContext
{
    public DbSet<Record> Records { get; set; }
    public DbSet<Shipping> Shippings { get; set; }
    public DbSet<Delivery> Deliveries { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {

        modelBuilder.Entity<Record>()
            .HasRequired(m => m.Shipping)
            .WithRequiredDependent(x => x.Record)
            .WillCascadeOnDelete(false);

        modelBuilder.Entity<Record>()
            .HasRequired(m => m.Delivery)
            .WithRequiredDependent(x => x.Record)
            .WillCascadeOnDelete(false);

        base.OnModelCreating(modelBuilder);
    }

主程序（第二次尝试）

---

为了避免额外的索引，不要在记录类中指定键字段。 要获取默认标识行为名称，请输入密钥字段Id

public class Record
{
    public Record()
    {
        Shipping = new Shipping();
        Delivery = new Delivery();
    }

    public int Id { get; set; }
    public virtual Shipping Shipping { get; set; }
    public virtual Delivery Delivery { get; set; }
}

using (Context context = new Context())
      {               
            var model = context.Records.Create();
            model.Shipping = context.Shippings.Create();
            var shipping = model.Shipping;
            shipping.ShippingName = "TestContext";
            model.Delivery = context.Deliveries.Create();
            var delivery = model.Delivery;
            delivery.DeliveryText = "customText";
            context.Entry(model).State = EntityState.Added;
            context.SaveChanges();
      }

public class Record
{
    public Record()
    {
        Shipping = new Shipping();
        Delivery = new Delivery();
    }

    public int Id { get; set; }
    public virtual Shipping Shipping { get; set; }
    public virtual Delivery Delivery { get; set; }
}