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POUsing custom ModelBinder to have strongly typed TPH models in controller actions-- is this smelly?
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copied!<p>Here's a little background on my solution:</p> <ul> <li>ASP.Net MVC app</li> <li>Using Linq-to-SQL with table-per-hierarchy inheritance</li> <li>Using DataAnnotationsModelBinder as default</li> </ul> <p>So I have a <code>Device</code> abstract class and then a series of derived classes (<code>ServerDevice</code>, <code>DiskDevice</code>, <code>PSUDevice</code>, etc) that inherit from it in the proscribed Linq-to-SQL way. I have one controller that handles all these different related model types, and it renders different partials based on the type and a handy drop down to select them. My (GET) Create method looks like this:</p> <pre><code>// GET: /Devices/Create/3 public ActionResult Create(int? deviceTypeID) { return View(DeviceFactory(deviceTypeID); } </code></pre> <p>Where <code>DeviceFactory</code> is a static method returns a new instance of one of the derived classes based on an int discriminator. The POST Create method looks like this:</p> <pre><code>// POST: /Devices/Create [AcceptVerbs(HttpVerbs.Post)] public ActionResult Create([ModelBinder(typeof(DeviceModelBinder))]Device device) { if (!ModelState.IsValid) return View(device); _repository.Add(device); _repository.Save(); TempData["message"] = string.Format("Device was created successfully."); return RedirectToAction(Actions.Index); } </code></pre> <p>and my custom model binder looks like this:</p> <pre><code>public class DeviceModelBinder : DataAnnotationsModelBinder { private readonly Dictionary<string, Type> _deviceTypes = new Dictionary<string, Type> { {"1", typeof (ServerDevice)}, {"2", typeof (DiskDevice)} // And on and on for each derived type }; protected override object CreateModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Type modelType) { return base.CreateModel(controllerContext, bindingContext, _deviceTypes[bindingContext.ValueProvider["deviceTypeID"].AttemptedValue]); } } </code></pre> <p>So after trying to hook this up all day, reading about ActionInvoker, custom ActionFilters, and all sorts of other MVC stuff, I'm wondering if the solution I've arrived at is a good one. Help allay my fears that I'm missing some hugely obvious concept and re-inventing the wheel. <strong>Is there a better or more concise way?</strong></p> <p>Thanks!</p>

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