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POWCF RIA EntityQuery returns null for Foreign Keys
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  1. POWCF RIA EntityQuery returns null for Foreign Keys
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    copied!<p>I'm following a <a href="http://www.silverlightshow.net/items/Working-with-Prism-4-Part-3-Composite-Command-and-Pub-Sub-Events.aspx" rel="nofollow noreferrer">tutorial</a> on Silverlight and Prism, where <strong>WCF RIA Services</strong> are uses to access the <strong>Northwind database</strong> through an <strong>ADO.NET Entity Data Model</strong>.</p> <p>In the Northwind database, there is a table Order_Details which is connected to two other tables (Orders and Products) via foreign keys:</p> <p><img src="https://i.stack.imgur.com/iTm74.png" alt="Picture of Data Model"></p> <p>The code to query the database looks like this:</p> <pre><code>EntityQuery&lt;Order_Detail&gt; detailQuery = _MyDomainContext.GetOrder_DetailsQuery(); _MyDomainContext.Load(detailQuery.Where( det =&gt; det.Order.Customer.CustomerID == cust.CustomerID).OrderByDescending( det =&gt; det.Order.OrderDate).Take(10), OnDetailsLoaded, null); </code></pre> <p>and then in OnDetailsLoaded:</p> <pre><code>var details = loadOp.Entities; if (details != null) { var detailsList = details.ToList(); detailsList.ForEach(det =&gt; Orders.Add( new OrderItem { ProductName = det.Product.ProductName, Quantity = det.Quantity, OrderDate = det.Order.OrderDate.Value })); </code></pre> <p>This gives me a Null Exception at <code>new OrderItem</code>, because both Product and Order are null. I have set my EntityDataModel to "Include Foreign Key Columns in the Model". The code is exactly as in the tutorial, I only had to recreate the ADO.Net EntityDataModel and the DomainService to work with my local database, so the error is probably somewhere there.</p> <p>How would I debug this error? I have no previous experience with databases. I'm using SQL Server 2012 with a Northwind database adapted for 2012, while the tutorial was written with SQL Server 2008 RC.</p>
 

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