无法让 EF4 预加载子类实体正常工作
我的 EF4 模型中有一个抽象的 Content 实体，它有一个具体的子类 MultipleChoiceItem。在 MultipleChoiceItem 的情况下，有一个相关表，可通过 MultipleChoiceItem 实体上的导航属性访问，称为“选项”。我想立即加载选项结果，因为如果您获得 MultipleChoiceItem，您总是需要选项。但是，我似乎无法让它发挥作用。这是我基本上所做的：
MultipleChoiceItem 是一个子类，因此它没有默认创建的元数据。因此，我为其创建了一个元数据类，如下所示：
[MetadataTypeAttribute(typeof(MultipleChoiceItem.ContentMetadata))] 公共部分类 MultipleChoiceItem { 内部密封类 MultipleChoiceItemMetadata { ...其他东西... [包括] 公共EntityCollection选项{获取;放; } ...其他东西... } 然后我在 ContentService 中创建了一个新查询，如下所示：
public IQueryable;获取多项选择项() { 返回 this.ObjectContext.Contents.OfType () .include("选项"); }
在单元测试中，我这样调用它：
context = new ContentContext();
var loadOperation = context.Load(context.GetMultipleChoiceItemsQuery());
loadOperation.Completed += new EventHandler(CompletedHandler);
一旦进入 CompletedHandler，以下代码似乎不会加载了Options属性——事实上，Options.Count == 0，而它应该是4（通过检查底层数据存储来验证）。
MultipleChoiceItem mci = context.Contents.First(c => c.ContentId == mciId) as MultipleChoiceItem;
谁能告诉我我做错了什么？我试图遵循我看到的发布的模型，但显然遗漏了一些东西......
谢谢！
I have an abstract Content entity in my EF4 model with a concrete subclass, MultipleChoiceItem. There is a related table in the case of MultipleChoiceItem accessed by a Navigation property on the MultipleChoiceItem entity called Options. I would like to eager-load the Options result because if you're getting a MultipleChoiceItem, you always want the Options. However, I can't seem to get this to work. Here is what I've bascially done:
The MultipleChoiceItem is a subclass, therefore it didn't get metadata created by default. So, I created a metadata class for it that looks sort of like this:
[MetadataTypeAttribute(typeof(MultipleChoiceItem.ContentMetadata))] public partial class MultipleChoiceItem { internal sealed class MultipleChoiceItemMetadata { ... other stuff ... [Include] public EntityCollection<McOption> Options { get; set; } ... other stuff ... }I then created a new query in the ContentService that looks like this:
public IQueryable<Content> GetMultipleChoiceItems() { return this.ObjectContext.Contents.OfType<MultipleChoiceItem>() .Include("Options"); }
In a unit test, I'm calling that like this:
context = new ContentContext();
var loadOperation = context.Load(context.GetMultipleChoiceItemsQuery());
loadOperation.Completed += new EventHandler(CompletedHandler);
Once I get into the CompletedHandler, the following code doesn't seem to have the Options property loaded--in fact, Options.Count == 0 when it should be 4 (verified by checking the underlying data store).
MultipleChoiceItem mci = context.Contents.First(c => c.ContentId == mciId) as MultipleChoiceItem;
Can anyone tell me what I'm doing wrong? I've tried to follow the models I've seen posted and am apparently missing something...
Thanks!
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我必须手动完成的元数据的元数据类型属性（因为出于某种原因，RIA 默认情况下不会为子类创建元数据）的类型错误。它无意中读到：
并且应该读到：
没有为子类生成元数据的事实是相当烦人的。
无论如何，在这里发帖以防其他人遇到这个问题！
My metadata type attribute for the metadata that I had to do by hand (since RIA doesn't make metadata for subclasses by default for some reason) had the wrong type. It inadvertantly read:
And should have read:
The fact that there is no metadata generated for subclasses is quite annoying.
Anyhow, posting here in case anyone else has this issue!