EF CTP5-强类型热切加载-如何包括嵌套的导航属性? [英] EF CTP5 - Strongly-Typed Eager Loading - How to Include Nested Navigational Properties?

问题描述

试图将我们的EF4解决方案转换为EF CTP5，并遇到问题.

Attempting to cutover our EF4 solution to EF CTP5, and ran into a problem.

这是模型的相关部分:

相关关系: -一个县有许多城市 -单个城市具有一个单个州

The pertinent relationship: - A single County has many Cities - A single City has a single State

现在，我要执行以下查询: -获取系统中的所有县，并包括所有城市以及这些城市的所有州.

Now, i want to perform the following query: - Get all Counties in the system, and include all the Cities, and all the State's for those Cities.

在EF4中，我会这样做:

In EF4, i would do this:

var query = ctx.Counties.Include("Cities.State");

在EF CTP5中，我们有一个强类型的包含，它包含一个Expression<Func<TModel,TProperty>>.

In EF CTP5, we have a strongly typed Include, which takes an Expression<Func<TModel,TProperty>>.

我可以毫无问题地获得该县的所有城市:

I can get all the Cities for the County no problem:

var query = ctx.Counties.Include(x => x.Cities);

但是我如何才能获得这些城市的州?

But how can i get the State for those Cities too?

我使用的是纯POCO，所以County.Cities是ICollection<City>，因此我不能这样做:

I am using pure POCO's, so County.Cities is an ICollection<City>, therefore i cannot do this:

var query = ctx.Counties.Include(x => x.Cities.State)

由于ICollection<City>没有名为State的属性.

几乎就像我需要使用嵌套的IQueryable.

It's almost like i need to use a nested IQueryable.

有什么想法吗?在这种情况下，我是否需要退回到魔术字符串包括"?

Any ideas? Do i need to fallback to the magic string Include in this scenario?

推荐答案

为此，您可以使用 Select 方法:

For that you can use you the Select method:

var query = ctx.Counties.Include(x => x.Cities.Select(c => c.State))

此处 可以找到另一个例子.

Here you can find another example.

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