Question

我首先使用的是Entity Framework 4.1代码，我有两个实体和一个两个实体都从中继承的抽象类。

public abstract class Customer
{
    public long CustomerId { get; set; }
    public string Rating { get; set; }
    public int FinancialStatusValue { get; internal set; }
}

public class Organization : Customer
{
    public string Name { get; set; }
    public string Name2 { get; set; }
    public string LegalName { get; set; }
    public string OrganizationNumber { get; set; }
    public string Vat { get; set; }
    public string Duns { get; set; }
    public Organization HeadQuarter { get; set; }
    public virtual ICollection<Organization> ChildOrganizations { get; set; }
}

我用我的模型映射：

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
        modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();

        modelBuilder.Entity<Customer>().ToTable("Customer");
        modelBuilder.Entity<Organization>().ToTable("Organization");

        modelBuilder.Entity<Organization>().HasOptional(h => h.HeadQuarter)
            .WithMany(c => c.ChildOrganizations)
            .HasForeignKey(o => o.ParentId);

 }

然后我使用以下方式查询组织：

var org = ctx.Customers.OfType<Organization>().Single(c => c.CustomerId == 259033);

填充了ParentId，但HeadQuarter和ChildOrganizations始终为空。

我错过了什么？

Answer 1

您可以使用Include

来急切加载导航属性

var org = ctx.Customers.OfType<Organization>()
    .Include(o => o.HeadQuarter)
    .Include(o => o.ChildOrganizations)
    .Single(c => c.CustomerId == 259033);

您还可以利用延迟加载，这会在您第一次访问时加载导航属性。您必须将导航属性声明为virtual。（您仅对ChildOrganizations执行此操作，但对HeadQuarter执行此操作。）

请注意，Include只会加载您准确指定的导航属性。它不会加载整个树结构，即不加载Organization.ChildOrganizations.ChildOrganizations等等。

实体框架中的自引用关系

1 个答案: