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POEF4 model referencing through result foreign keys using linq to entities
 

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    <p>Using one big EF4 model I'm trying to do some of the same things, that can be done in linq2sql using separate dbml's. A basic issue I have run into, which is likely a very fundamental lack of knowledge of linq to entities on my behalf, is how do you use result references to find objects in tables that are referenced?</p> <p>Example, I have 4 tables that are all linked together through foreign keys.</p> <p>Conceptually I can hop through all of the tables using foreach on the result references, however it seems pretty clumsy, how could below code be written using linq instead?</p> <pre><code> //Get book var book= db.books.SingleOrDefault(d =&gt; d.bookId == 286); //If no book, return if (book == null) return null; //Get the shelf associated with this book List&lt;shelf&gt; slist = new List&lt;shelf&gt;(); foreach (reading r in book.readings) { foreach (event re in r.events) { slist.Add(re); } } List&lt;event&gt; bookevents = slist.Distinct().ToList(); //Get the customers associated with the events List&lt;int&gt; clist = new List&lt;int&gt;(); foreach (event eb in bookevents) { var cust = db.customers.Where(c =&gt; c.customerID == eb.inID || c.customerID == eb.outID).ToList(); clist.AddRange(cust.Select(c =&gt; c.customerID)); } //Return the list of customers return clist; </code></pre> <p>EDIT: I got it down to 3 steps, posting this in case other people run into similar issues. I welcome any comments on how to do this more elegantly</p> <pre><code> //Get book var book= db.books.SingleOrDefault(d =&gt; d.bookId == 286); //If no book, return if (book == null) return null; //Get the bookevents associated with this book var bookevents = (from reading in book.readings select reading.events).SelectMany(e =&gt; e).Distinct(); //Get the customers associated with the events var clist = (from be in bookevents from c in db.customers where c.customerID == be.inID || c.customerID == be.outID select c.customerID).ToList(); //Return the list of customers return clist; </code></pre>
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