实体框架：如何做正确的"包括"在自定义类型 [英] Entity Framework: how to do correct "Include" on custom type

问题描述

假设我们有2种，通过EF 4映射到数据库。

Suppose we have 2 types, mapped to a Database via EF 4.

Schedule 1.....1 Visit

此外，我们还有第三个自定义视图类型

Also, we have third custom view type

public class ScheduleView
{
    public Schedule Schedule { get; set; }
    public Visit Visit { get; set; }
}

所以，我们可以这样写连接查询

So we can write the join query

var query = Context.Schedule.Join(Context.Visit
,/*Schedule join key definition*/,/*Visit join key definition*/,
(scheduleView, visit) => new ScheduleView {Schedule = scheduleView, Visit = visit})

问题是，我也需要加载患者 访问的财产键入。但是，当我写

The problem is that I need to load also Patient property of Visit type. But when I write

query = (query as ObjectQuery<ScheduleView>).Include("Visit.Patient");

我收到运行时错误

I receive a runtime error

无法转换类型
'System.Linq.IQueryable 1键入
'System.Data.Objects.ObjectQuery 1。
LINQ到实体仅支持铸造
实体数据模型的基本类型

Unable to cast the type 'System.Linq.IQueryable1' to type 'System.Data.Objects.ObjectQuery1'. LINQ to Entities only supports casting Entity Data Model primitive types.

所以，问题是 - 怎么样？强制查询，以包括我的自定义类型中的东西。

So, the question is - how to force query to include something within my custom type?

推荐答案

最后，开发了一些丑陋的解决方法 - 在自定义类型引入了新的成员， 。显式查询，它

Finally, developed some ugly workaround - introduced new member in custom type and explicitly queried for it.

public class ScheduleView
{
    public Schedule Schedule { get; set; }
    public Visit Visit { get; set; }
    **public Patient Patient{ get; set; }**
}

    var query = Context.Schedule.Join(Context.Visit
    ,/*Schedule join key definition*/,/*Visit join key definition*/,
    (scheduleView, visit) => new ScheduleView 
{Schedule = scheduleView, Visit = visit, **Patient = visit.Patient**})

现在我有患者正确加载在我的自定义类型。有趣的，但是当我调查 ScheduleView.Visiting.Patient 引入后 ScheduleView.Patient 我发现它也装载。
不能得到的EF逻辑，在这种情况下。而且不知道如何强制加载 ScheduleView.Visiting.Patient 而无需加载无用 ScheduleView.Patient ：（

Now I have Patient loading properly in my custom type. Amusing, but when I investigate ScheduleView.Visiting.Patient after introducing ScheduleView.Patient I found it also loaded. Cant get the EF logic in this case. And dunno how to force loading ScheduleView.Visiting.Patient without having to load useless ScheduleView.Patient :(

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