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POCan't Get EF4 Eager Loading of Subclassed Entities to Work
 

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  1. POCan't Get EF4 Eager Loading of Subclassed Entities to Work
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    <p>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:</p> <ul> <li><p>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: </p> <pre><code>[MetadataTypeAttribute(typeof(MultipleChoiceItem.ContentMetadata))] public partial class MultipleChoiceItem { internal sealed class MultipleChoiceItemMetadata { ... other stuff ... [Include] public EntityCollection&lt;McOption&gt; Options { get; set; } ... other stuff ... } </code></pre></li> <li><p>I then created a new query in the ContentService that looks like this: </p> <pre><code>public IQueryable&lt;Content&gt; GetMultipleChoiceItems() { return this.ObjectContext.Contents.OfType&lt;MultipleChoiceItem&gt;() .Include("Options"); } </code></pre></li> </ul> <p>In a unit test, I'm calling that like this:</p> <pre><code> context = new ContentContext(); var loadOperation = context.Load(context.GetMultipleChoiceItemsQuery()); loadOperation.Completed += new EventHandler(CompletedHandler); </code></pre> <p>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).</p> <pre><code> MultipleChoiceItem mci = context.Contents.First(c =&gt; c.ContentId == mciId) as MultipleChoiceItem; </code></pre> <p>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...</p> <p>Thanks!</p>
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    1. PTQuestion
    1. USDavid Moye
    1. USDavid Moye
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    1. This table or related slice is empty.
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    1. PO
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    1. COI don't see where you use the GetMultipleChoiceItems? Your last code snippets simply access Contents without using Include.
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      1. POCan't Get EF4 Eager Loading of Subclassed Entities to Work
      1. USLadislav Mrnka
    2. COI'm using it in the context.Load in the snippet before that one. The last snippet is in the event handler that happens at Completed time for the loadOperation.
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      1. POCan't Get EF4 Eager Loading of Subclassed Entities to Work
      1. USDavid Moye
 

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