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    <p>Figured it out - wasn't easy, so i'll try to explain best i can. (for those who care)</p> <p><strong>Controller Relevant Code:</strong></p> <pre><code>// _userContentService is IUserContentService _userContentService.Update(review); </code></pre> <p>So, my controller calls a method called <code>Update</code> on <code>IUserContentService</code>, passing through the strongly-typed <code>Review</code> object.</p> <p><strong>User Content Service Relevant Code</strong></p> <pre><code>public void Update(Post post) { // _userContentRepository is IPostRepository _userContentRepository.UpdateModel(post); } </code></pre> <p>So, my service calls a method called <code>UpdateModel</code> on <code>IPostRepository</code>, passing through the strongly-typed <code>Review</code> object.</p> <p>Now, here is the tricky part.</p> <p>I actually have <strong>no specific Repositories</strong>. I have a <em>generic repository</em> called <code>GenericRepository&lt;T&gt; : IRepository&lt;T&gt;</code>, which handles <strong>all the different repositories.</strong></p> <p>So when something requests a <code>IPostRepository</code> (which my service was doing), DI would give it a <code>GenericRepository&lt;Post&gt;</code>.</p> <p>But now, i give it a <code>PostRepository</code>:</p> <pre><code>public class PostRepository : GenericRepository&lt;Post&gt;, IPostRepository { public void UpdateModel(Post post) { var originalPost = CurrentEntitySet.SingleOrDefault(p =&gt; p.PostId == post.PostId); Context.ApplyCurrentValues(GetEntityName&lt;Post&gt;(), post); } } </code></pre> <p>And because the class <em>derives</em> from <strong>GenericRepository</strong>, it inherits all the core repository logic (Find, Add, etc).</p> <p>At first, i tried to put that <strong>UpdateModel</strong> code in the <strong>GenericRepository</strong> class itself (and then i wouldn't have needed this specific repository), but the problem is the logic to retrieve the existing entity is based on a specific entity key, which the <code>GenericRepository&lt;T&gt;</code> would not know about.</p> <p>But the end result is the <em>stitching</em> is hidden deep down in the depths of the data layer, and i end up with a really clean Controller.</p> <p><strong>EDIT</strong></p> <p>This "stub technique" also works:</p> <pre><code>public void UpdateModel(Post post) { var stub = new Review {PostId = post.PostId}; CurrentEntitySet.Attach(stub); Context.ApplyCurrentValues(GetEntityName&lt;Post&gt;(), post); } </code></pre> <p>But the problem is because <strong>Post</strong> is abstract, i cannot instantiate and therefore would have to check the type of Post and create stubs for <em>every single</em> derived type. Not really an option.</p> <p><strong>EDIT 2 (LAST TIME)</strong></p> <p>Okay, got the "stub technique" working with abstract classes, so now the concurrency issue is solved.</p> <p>I added a generic type parameter to my <strong>UpdateModel</strong> method, and the special <strong><a href="http://msdn.microsoft.com/en-us/library/sd2w2ew5(VS.80).aspx" rel="nofollow noreferrer">new() constraint</a></strong>.</p> <p><strong>Implementation:</strong></p> <pre><code>public void UpdateModel&lt;T&gt;(T post) where T : Post, new() { var stub = new T { PostId = post.PostId }; CurrentEntitySet.Attach(stub); Context.ApplyCurrentValues(GetEntityName&lt;Post&gt;, post); } </code></pre> <p><strong>Interface:</strong></p> <pre><code>void UpdateModel&lt;T&gt;(T post) where T : Post, new(); </code></pre> <p>This prevents me from having to figure out the type of T manually, prevents concurrency issues and also prevents an extra trip to the DB.</p> <p>Pretty groovy.</p> <p><strong>EDIT 3 (i thought the last time was the last time)</strong></p> <p>The above "stub technique" works, but if i retrieve the object beforehand, it throws an exception stating an entity with that key already exists in the OSM.</p> <p>Can anyone advise how to handle this?</p> <p><strong>EDIT 4 (OK - this is it!)</strong></p> <p>I found the solution, thanks to this SO answer: <a href="https://stackoverflow.com/questions/1715501/is-is-possible-to-check-if-an-object-is-already-attached-to-a-data-context-in-ent/1716109#1716109">Is is possible to check if an object is already attached to a data context in Entity Framework?</a></p> <p>I had tried to "check if the entity is attached" using the following code:</p> <pre><code>ObjectStateEntry entry; CurrentContext.ObjectStateManager.TryGetObjectStateEntry(entity, out entry); </code></pre> <p>But it always returned <strong>null</strong>, even through when i explored the OSM i could see my entity there with the same key.</p> <p>But this code works:</p> <pre><code>CurrentContext.ObjectStateManager.TryGetObjectStateEntry(CurrentContext.CreateEntityKey(CurrentContext.GetEntityName&lt;T&gt;(), entity), out entry) </code></pre> <p>Maybe because i'm using Pure POCO's, the OSM had trouble figuring out the entity key, who knows.</p> <p>Oh and one other thing i added - so that i don't have to add a specific repository for each entity, i created an attribute called "<strong>[EntityKey]</strong>" (public property attribute).</p> <p>All POCO's must have 1 public property decorated with that attribute, or i throw an exception in my repository module.</p> <p>So my generic repository then looks for this property in order to create/setup the stub.</p> <p>Yes - it uses reflection, but it's clever reflection (attribute-based) and i'm already using reflection for plularization of entity set names from T.</p> <p>Anyway, problem solved - all working fine now!</p>
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    1. COLooks interesting, nice of you to have posted such a detailed description of your solution. One issue, however - doesn't **Attach** throw an exception if a *Post* with the same *PostId* is already attached? E.g. if you do a *GetAll()* against the same context at some point earlier and all the Posts are already attached?
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    2. COHmm, that's a good point - i'll test that out by doing exactly that (when i get in the office on monday). If so i might have to check is an entity is already attached, though i'm not really sure how to do that. (esp since im using pure pocos)
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    3. CO@Yakimych - dang, your right. If i retrieve that object beforehand it throws the exception. Any ideas? Is there a way we can "check if an entity is already attached to the graph?" I might have to ask another question.
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