如何在Entity Framework 5中包含子对象的子对象

Question

我正在使用Entity Framework 5 code first和ASP.NET MVC 3.

我正在努力让一个子对象的子对象填充.以下是我的课程..

申请类;

public class Application
{
     // Partial list of properties

     public virtual ICollection<Child> Children { get; set; }
}

儿童班:

public class Child
{
     // Partial list of properties

     public int ChildRelationshipTypeId { get; set; }

     public virtual ChildRelationshipType ChildRelationshipType { get; set; }
}

ChildRelationshipType类:

public class ChildRelationshipType
{
     public int Id { get; set; }

     public string Name { get; set; }
}

存储库中GetAll方法的一部分,用于返回所有应用程序:

return DatabaseContext.Applications
     .Include("Children");

Child类包含对ChildRelationshipType类的引用.要与应用程序的孩子一起工作,我会有这样的事情:

foreach (Child child in application.Children)
{
     string childName = child.ChildRelationshipType.Name;
}

我在这里得到一个错误,即对象上下文已经关闭.

如何指定每个子对象必须包含ChildRelationshipType像我上面所做的那样的对象？

Answer 1

如果包含库System.Data.Entity,则可以使用Include()方法的重载,该方法采用lambda表达式而不是字符串.然后Select(),您可以使用Linq表达式而不是string路径来覆盖孩子.

return DatabaseContext.Applications
     .Include(a => a.Children.Select(c => c.ChildRelationshipType));

Answer 2

使用.NET Core中的EF Core,您可以使用以下关键字ThenInclude:

return DatabaseContext.Applications
 .Include(a => a.Children).ThenInclude(c => c.ChildRelationshipType);

包括儿童收藏中的儿童:

return DatabaseContext.Applications
 .Include(a => a.Childrens).ThenInclude(cs => cs.ChildRelationshipType1)
 .Include(a => a.Childrens).ThenInclude(cs => cs.ChildRelationshipType2);

Answer 3

我最终做了以下工作:

return DatabaseContext.Applications
     .Include("Children.ChildRelationshipType");