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copied!<p>I would rethink your Entity Framework model.</p> <p>That domain model you have provided looks perfect for <strong>Table-per-type Inheritance</strong>.</p> <p>Then you could use the LINQ <code>.OfType<T>()</code> method to filter different transaction types, based on a generic type parameter on your Repository:</p> <pre><code>public class TransactionRepository : IRepository<Transaction> { public TTransaction Find<TTransaction>(int transactionId) where TTransaction : TransactionBase, new() { return _ctx.Transactions.OfType<TTransaction>().SingleOrDefault(tran => tran.TransactionId == transactionId); } } </code></pre> <p>Then you could do this:</p> <pre><code>var ccTran = _repository.Find<CreditCardTransaction>(x => x.TransactionId == 1); var cTran = _repository.Find<CheckTransaction>(x => x.TransactionId == 2); </code></pre> <p>As for your questions:</p> <blockquote> <p>So, the client should be able to search on CardNumber, RoutingNumber, Amount, etc., all from one method</p> </blockquote> <p>I don't think that's possible with one method, well certainly not without some kind of if/switch statement. </p> <p>The kicker is the filtering - it all comes down to the signature of the repository method - what is provided, what generic constraints, etc.</p> <p>If your saying each sub-type has it's own repository, then does it really make sense to have a single method which serves all three repositories? Where should this magical method live?</p> <p>So overall, i think you've reached the point many have reached, where your domain is fighting against Entity Framework.</p> <p>Basically, if your working on an objectset of type AbstractA, you can't "downcast" to a objectset of type DerivedA in order to do the filtering.</p> <p>It comes down to how much of your domain model your willing to compromise. I myself had a similar problem, and i ended up using TPT inheritance (then switching to TPH because the performance was better).</p> <p>So without knowing too much about your domain other than what you've mentioned, i think you need to re-think the statement "Each sub-class has it's own repository since each has its own properties and way of being fetched".</p> <p>It looks like you should have a single repository, TPT/TPH in your EF model, and the "search" method on your Repository with a generic type constraint on the transaction type.</p> <p>If your gun-ho on having the magic single method, you would need a nasty switch/if statement, and delegate the filtering to a specific method.</p>

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