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POIncluding navigation properties from Entity Framework TPH classes
 

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  1. POIncluding navigation properties from Entity Framework TPH classes
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    <p>I've got an EF hierarchy that (dramatically simplified) looks something like this:</p> <pre><code>class Room { EntityCollection&lt;Session&gt; Sessions; } class Session { EntityCollection&lt;Whiteboard&gt; Whiteboards; EntityReference Room; } class Whiteboard { EntityCollection&lt;WhiteboardShape&gt; WhiteboardShapes; EntityReference Session; } abstract class WhiteboardShape { EntityReference Whiteboard; } class WhiteboardShapeEllipse : WhiteboardShape { } class WhiteboardShapePolyline { WhiteboardShape { EntityCollection&lt;PolylinePoint&gt; PolylinePoints } class PolylinePoint { EntityReference&lt;WhiteboardShapePolyline&gt; WhiteboardShapePolylineReference; } </code></pre> <p>In other words, a Room can contain multiple sessions; each Session can contain multiple Whiteboards; and each Whiteboard can contain multiple WhiteboardShapes. These shapes can be of various types, including a WhiteboardShapePolyline, which itself can contain multiple PolylinePoints.</p> <p>When a remote user initially connects to the room, I need to pass the entire object graph to that user, and I'm trying to figure out how to load that graph from the database into memory as efficiently as possible.</p> <p>Now, of course, the EF allows for you to do eager loading, like so:</p> <pre><code> Room room = ctx.Room .Include("Sessions.Whiteboards") .FirstOrDefault(r =&gt; r.OwnerID == ownerUserID &amp;&amp; r.Name == roomName); </code></pre> <p>But Include() doesn't let me load up the PolylinePoints. Specifically, if I try:</p> <pre><code> Room room = ctx.Room .Include("Sessions.Whiteboards.WhiteboardShape.PolylinePoint") .FirstOrDefault(r =&gt; r.OwnerID == ownerUserID &amp;&amp; r.Name == roomName); </code></pre> <p>I get the exception "A specified Include path is not valid. The EntityType 'SlideLinc.Model.WhiteboardShape' does not declare a navigation property with the name 'PolylinePoint'." </p> <p>Nor does this work: </p> <pre><code>.Include("Sessions.Whiteboards.WhiteboardShapePolyline.PolylinePoint") </code></pre> <p>Nor does this:</p> <pre><code>.Include("Sessions.Whiteboards.WhiteboardShape.WhiteboardShapePolyline.PolylinePoint") </code></pre> <p>Nor any other way of framing the navigation path that I can think of.</p> <p>The way that I've ended up doing it sure <i>seems</i> like a hack to me:</p> <pre><code> // Make sure we've got everything loaded. if (room != null) { if (!room.Sessions.IsLoaded) { room.Sessions.Load(); } foreach (Session session in room.Sessions) { if (!session.Whiteboards.IsLoaded) { session.Whiteboards.Load(); } foreach (Whiteboard whiteboard in session.Whiteboards) { if (!whiteboard.WhiteboardShape.IsLoaded) { whiteboard.WhiteboardShape.Load(); } foreach (WhiteboardShape shape in whiteboard.WhiteboardShape) { if (shape is WhiteboardShapePolyline) { WhiteboardShapePolyline polyline = (WhiteboardShapePolyline)shape; if (!polyline.PolylinePoints.IsLoaded) { polyline.PolylinePoints.Load(); } } } } } } </code></pre> <p>It works, but it's a lot more code than I want, and it's a whole bunch more database accesses than I want. </p> <p>The closest answer I've found is <a href="https://stackoverflow.com/questions/944332/entity-framework-inheritance-and-include">here</a>, but my poor Linq-starved brain can't figure out how to translate the example code into the more complicated hierarchy that I've got; plus, the sample code at that link is damned ugly and difficult to understand. I don't really want my entire object hierarchy depending on an obscure and invisible side-effect of how the EF internally constructs its hierarchies.</p> <p>Any other suggestions?</p>
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