如何在Entity Framework 5中包含子对象的子对象 [英] How to include a child object's child object in Entity Framework 5

问题描述

我正在使用实体框架5代码首先和 ASP.NET MVC 3 。

我正在努力获取一个子对象的子对象来填充。以下是我的课程。

应用程序类;

  public class应用程序
 {
 //部分属性列表
 
 public virtual ICollection< Child>孩子{get;组; 
} 
  

小孩类：

  public class Child 
 {
 //部分属性列表
 
 public int ChildRelationshipTypeId {get;组; } 
 
 public virtual ChildRelationshipType ChildRelationshipType {get;组; } 
} 
  

ChildRelationshipType类：

  public class ChildRelationshipType 
 {
 public int Id {get;组; } 
 
 public string Name {get;组; } 
} 
  

存储库中GetAll方法的一部分返回所有应用程序： p>

  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，我将会有这样的一些：

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

我在这里收到一个错误，表明对象上下文已经关闭。 >

如何指定每个子对象必须像上面那样包含 ChildRelationshipType 对象？

解决方案

如果您包含库 System.Data.Entity ，可以使用 Include（）方法，它采用lambda表达式而不是字符串。然后，您可以使用Linq表达式而不是 string 路径的小孩选择（）。

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

I am using Entity Framework 5 code first and ASP.NET MVC 3.

I am struggling to get a child object's child object to populate. Below are my classes..

Application class;

public class Application
{
     // Partial list of properties

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

Child class:

public class Child
{
     // Partial list of properties

     public int ChildRelationshipTypeId { get; set; }

     public virtual ChildRelationshipType ChildRelationshipType { get; set; }
}

ChildRelationshipType class:

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

     public string Name { get; set; }
}

Part of GetAll method in the repository to return all the applications:

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

The Child class contains a reference to the ChildRelationshipType class. To work with an application's children I would have something like this:

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

I get an error here that the object context is already closed.

How do I specify that each child object must include the ChildRelationshipType object like what I did above?

解决方案

If you include the library System.Data.Entity you can use an overload of the Include() method which takes a lambda expression instead of a string. You can then Select() over children with Linq expressions rather than string paths.

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

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