孙子藏品在EF 4.1明确加载 [英] Explicit loading of grandchild collections in EF 4.1

问题描述

考虑下面的模型......

Given the following model ...

public class Parent
{
    public int Id { get; set; }
    public ICollection<Child> Children { get; set; }
}

public class Child
{
    public int Id { get; set; }
    public ICollection<Grandchild> Grandchildren { get; set; }
}

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

...我们能贪婪加载与包含 A 父所有孩子和孙子一步到位，像这样：

... we can eager load with Include a Parent with all Children and Grandchildren in one step like so:

context.Parents.Include(p => p.Children.Select(c => c.Grandchildren))

是类似的东西可能对于明确加载

子集合可以明确地装载这种方式：

The child collection can be explicitely loaded this way:

Parent parent = context.Parents.Find(parentId);
context.Entry(parent).Collection(p => p.Children).Load();

但尝试加载孩子以同样的方式与包含 ...

context.Entry(parent)
    .Collection(p => p.Children.Select(c => c.Grandchildren)).Load();

...不编译UND 收集的字符串超载 ...

context.Entry(parent).Collection("Children.Grandchildren").Load();

...抛出一个异常（...不允许有虚线路径......）。

... throws an exception ("...no dotted paths allowed...").

我发现工作的唯一一件事就是明确地加载孙子在一个循环：

The only thing which I found working is to explicitely load the Grandchildren in a loop:

Parent parent = context.Parents.Find(parentId);
context.Entry(parent).Collection(p => p.Children).Load();
foreach (var child in parent.Children)
    context.Entry(child).Collection(c => c.GrandChildren).Load();

我想知道如果我错过了什么，如果有一些其他的方式来明确地加载孙子在一个往返。

感谢您提前反馈！

推荐答案

正如我指出的评论，你可以尝试让查询的关系，再加入包括并执行装载。是这样的：

As I pointed in the comment you can try to get query for relation first, then add includes and execute loading. Something like:

context.Entry(parent)
       .Collection(p => p.Children)
       .Query()
       .Include(c => c.Grandchildren) // I'm not sure if you can include grandchild directly  
       .Load();

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