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POLook-up tables with Linq-to-Sql
 

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    <p>I'm working on a car dealer website at the moment, and I've been working on a 'Vehicle' model in my database. I've been making extensive use of lookup tables with FK relationships for things like Colour, Make, Model etc.</p> <p>So a basic version could be something like:</p> <pre><code>Vehicle { Id MakeId ModelId ColourId Price Year Odometer } </code></pre> <p>Which then uses a simple 2-column look-up table, for example Colour would have a ColourId column, and ColourText column; nothing unusual.</p> <p>This is all good and well, however I've found my generated Linq-to-Sql classes become more complex when you start using look-up tables. To get the colour I now have to do things like Vehicle.Colour.ColourText. Adding new vehicles requires looking up all the various tables to ensure the values are there, etc. So I don't really want to be passing this Linq-to-Sql model around the rest of my application code.</p> <p>So my current approach implements a couple of methods to convert this linq model into a pure domain model, which is nearly an identical object, but just replaces the Id fields with their actual textual values (strings). This is all wrapped up in a repository, so the rest of the app is only aware of these straight 'domain' objects, and not the data access objects. If the app needs to insert a new record, I pass this domain model back in to the repository, which then converts it back to the Linq-to-Sql variant, ensuring all the lookup values are in fact valid.</p> <p>Is this a decent idea? I feel a little dirty doing this conversion, it seems to go against one of the reasons for using Linq-to-Sql in the first place. Then again, I guess it would be even worse passing around objects exposing look-ups and the like to the rest of the app. Is this why more fully-fledged O/RMs are more widely used?</p> <p>Using the domain objects over the L2S ones also makes it easier for JSON serialisation for use with AJAX and the like too.</p> <p>I guess I'm just asking if the approach I've taken is reasonable? Cheers.</p>
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