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    <p>It would be a good design to have the storage/retrieval separate from the entity anyway. In OO terms this can be referred to as the Single Responsibility Principle. Your entity exists for some purpose (probably related to your domain). The storage of that entity is a separate responsibility that could change independent of the domain. (e.g. you could retrive it from a database, a web service or the file system).</p> <p>Static methods are not the only way to do this of course. You could create an interface at the save/retrive level and implement that interface for each of the entities. Then you could easily use those in a generic way without worrying a lot about the types.</p> <p>Adding some example code:</p> <pre><code>interface EntityGateway&lt;TEntity&gt; { TEntity Load(String id); void Save(TEntity entity); } public class XEntityGateway implements EntityGateway&lt;XEntity&gt; { XEntity Load(String id) { ... implementation details } void Save(XEntity entity) { ... implementation details } } XEntityGateway gw = new XEntityGateway(); XEntity entity = gw.Load("SOMEID"); // modify entity gw.Save(entity); </code></pre>
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    1. COOkay, I'm familiar with SRP. So, you are suggesting a whole separate set of small classes (one-to-one) to provide a layer of separation? Sounds fair, even if it creates a whole slew of "mirror" classes. Though don't I end up with the very same problem enforcing a static factory method on those classes? I'm a little unclear about your non-static suggestion... how a non-static solution would look.
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      1. USKevin P. Rice
    2. COIt might be a one-to-one between entity and mapper. There are a lot of common solutions to this captured in things like Patterns of Enterprise Application Architecture (PEAA). In a Table Data Gateway (for example) you could have an XEntityGateway. An instance of that would be created to save or load an XEntity. Each entity would follow the same pattern. When they are interface-driven instances instead of static, it will be much easier to test your system because you'll be able to mock out this data layer during unit testing.
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    3. COI think I'm following you as saying create another data access layer (DAL) for XML persistence that communicates with the entities as a repository only (which I think is the proper way of doing EF)? Keep in mind this is just a personal application--I like doing things "right" and want to learn, but probably won't be mocking and testing. A simple, but correct architecture is what I'm looking for along with learning a good practice pattern.
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