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POAdvantage of creating a generic repository vs. specific repository for each object?
 

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    <p>We are developing an ASP.NET MVC application, and are now building the repository/service classes. I'm wondering if there are any major advantages to creating a generic IRepository interface that all repositories implement, vs. each Repository having its own unique interface and set of methods.</p> <p>For example: a generic IRepository interface might look like (taken from <a href="https://stackoverflow.com/questions/291344/repository-pattern-vs-dal">this answer</a>):</p> <pre><code>public interface IRepository : IDisposable { T[] GetAll&lt;T&gt;(); T[] GetAll&lt;T&gt;(Expression&lt;Func&lt;T, bool&gt;&gt; filter); T GetSingle&lt;T&gt;(Expression&lt;Func&lt;T, bool&gt;&gt; filter); T GetSingle&lt;T&gt;(Expression&lt;Func&lt;T, bool&gt;&gt; filter, List&lt;Expression&lt;Func&lt;T, object&gt;&gt;&gt; subSelectors); void Delete&lt;T&gt;(T entity); void Add&lt;T&gt;(T entity); int SaveChanges(); DbTransaction BeginTransaction(); } </code></pre> <p>Each Repository would implement this interface, for example:</p> <ul> <li>CustomerRepository:IRepository</li> <li>ProductRepository:IRepository</li> <li>etc.</li> </ul> <p>The alternate that we've followed in prior projects would be:</p> <pre><code>public interface IInvoiceRepository : IDisposable { EntityCollection&lt;InvoiceEntity&gt; GetAllInvoices(int accountId); EntityCollection&lt;InvoiceEntity&gt; GetAllInvoices(DateTime theDate); InvoiceEntity GetSingleInvoice(int id, bool doFetchRelated); InvoiceEntity GetSingleInvoice(DateTime invoiceDate, int accountId); //unique InvoiceEntity CreateInvoice(); InvoiceLineEntity CreateInvoiceLine(); void SaveChanges(InvoiceEntity); //handles inserts or updates void DeleteInvoice(InvoiceEntity); void DeleteInvoiceLine(InvoiceLineEntity); } </code></pre> <p>In the second case, the expressions (LINQ or otherwise) would be entirely contained in the Repository implementation, whoever is implementing the service just needs to know which repository function to call. </p> <p>I guess I don't see the advantage of writing all the expression syntax in the service class and passing to the repository. Wouldn't this mean easy-to-messup LINQ code is being duplicated in many cases? </p> <p>For example, in our old invoicing system, we call</p> <pre><code>InvoiceRepository.GetSingleInvoice(DateTime invoiceDate, int accountId) </code></pre> <p>from a few different services (Customer, Invoice, Account, etc). That seems much cleaner than writing the following in multiple places:</p> <pre><code>rep.GetSingle(x =&gt; x.AccountId = someId &amp;&amp; x.InvoiceDate = someDate.Date); </code></pre> <p>The only disadvantage I see to using the specific approach is that we could end up with many permutations of Get* functions, but this still seems preferable to pushing the expression logic up into the Service classes.</p> <p>What am I missing?</p>
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