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PONon-keyed associations with Entity Framework
 

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  1. PONon-keyed associations with Entity Framework
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    <p>I am having problems setting up an association in entity framework between two tables where the association does not contain all the primary key values.</p> <p>e.g. I have two tables (this is a contrived example, but it is sufficient to represent my real database which I cannot change)</p> <pre><code>------Items------ ---Orders---- ----------------- ------------- * ItemId - * OrderId - * EffectiveDate - - OrderDate - - Name - - ItemId - ----------------- ------------- * denotes primary key field </code></pre> <p>Ideally I'd like a property on Orders that indicates the Item that was effective at OrderDate, but I could live with an association on Order to a collection of Items and then create a readonly property on Order that selected the correct Item.</p> <p>EDIT: The database and model will be read-only so read-only solutions are OK.</p> <p>Is this possible in entity framework? (or even LINQ to SQL?)</p> <p>I believe that it is possible using NHibernate (can anyone confirm?) but I keep hitting brick walls with entity framework. So far the only solution I have managed is to create a property in the partial class for Order that uses a '<a href="http://blogs.msdn.com/alexj/archive/2009/06/08/tip-24-how-to-get-the-objectcontext-from-an-entity.aspx" rel="nofollow">hack</a>' to access the ObjectContext from order and query the context.Items collection directly as such</p> <pre><code>private IEnumerable&lt;Item&gt; Items { get { var ctx = this.GetContext(); return from i in ctx.Items where i.ItemId == this.ItemId select i; } } public Item Item { get { return (from i in Items where i.EffectiveDate &lt;= this.OrderDate orderby i.EffectiveDate ascending select i).First(); } } </code></pre> <p>Is there a better solution?</p>
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