把entity的class属性改成public，不报null错误了，但是在关联属性还没有使用的时候就提前加载了关联属性，这不是延迟加载吧？

class Program
{
    static void Main(string[] args)
    {
        try
        {
            using (var efDbContext = new EfDbContext())
            {

                var customer = efDbContext.Customers.FirstOrDefault();

                var price = customer.Orders.FirstOrDefault().Price;

                efDbContext.SaveChanges();
            }

        }
        catch (Exception e)
        {
            Console.WriteLine(e);
            throw;
        }
        Console.ReadLine();
    }
}

class EfDbContext : DbContext
{
    public EfDbContext():base("name = ConnectionString")
    {
        Database.SetInitializer(new DropCreateDatabaseIfModelChanges<EfDbContext>());
    }

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

        modelBuilder.Entity<Order>().HasRequired(o => o.Customer).WithMany(o => o.Orders)
            .HasForeignKey(o => o.CustomerId).WillCascadeOnDelete(false);

        this.Configuration.ProxyCreationEnabled = true;
        this.Configuration.LazyLoadingEnabled = true;

        this.Configuration.AutoDetectChangesEnabled = true;
    }

    public IDbSet<Customer> Customers { get; set; }
    public IDbSet<Order> Orders { get; set; }
}

public class Customer
{
    public int Id { get; set; }
    public string Name { get; set; }
    public virtual ICollection<Order> Orders { get; set; }
}

public class Order
{
    public int Id { get; set; }
    public double  Price { get; set; }
    public int CustomerId { get; set; }
    public virtual Customer Customer { get; set; }
}