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    <p>It took me a good day to come up with an answer to a closely related problem - although I'm not sure it's precisely the same issue, I'm posting it here in case others are looking for a solution to the same exact problem.</p> <p>In my case, I have an abstract base-type for a number of different view-model types. So in the main view-model, I have a property of an abstract base-type:</p> <pre><code>class View { public AbstractBaseItemView ItemView { get; set; } } </code></pre> <p>I have a number of sub-types of AbstractBaseItemView, many of which define their own exclusive properties.</p> <p>My problem is, the model-binder does not look at the type of object attached to View.ItemView, but instead looks only at the declared property-type, which is AbstractBaseItemView - and decides to bind <em>only</em> the properties defined in the abstract type, ignoring properties specific to the concrete type of AbstractBaseItemView that happens to be in use.</p> <p>The work-around for this isn't pretty:</p> <pre><code>using System.ComponentModel; using System.ComponentModel.DataAnnotations; // ... public class ModelBinder : DefaultModelBinder { // ... override protected ICustomTypeDescriptor GetTypeDescriptor(ControllerContext controllerContext, ModelBindingContext bindingContext) { if (bindingContext.ModelType.IsAbstract &amp;&amp; bindingContext.Model != null) { var concreteType = bindingContext.Model.GetType(); if (Nullable.GetUnderlyingType(concreteType) == null) { return new AssociatedMetadataTypeTypeDescriptionProvider(concreteType).GetTypeDescriptor(concreteType); } } return base.GetTypeDescriptor(controllerContext, bindingContext); } // ... } </code></pre> <p>Although this change feels hacky and is very "systemic", it seems to work - and does not, as far as I can figure, pose a considerable security-risk, since it does <em>not</em> tie into CreateModel() and thus does <em>not</em> allow you to post whatever and trick the model-binder into creating just any object.</p> <p>It also works only when the declared property-type is an <em>abstract</em> type, e.g. an abstract class or an interface.</p> <p>On a related note, it occurs to me that other implementations I've seen here that override CreateModel() probably will <em>only</em> work when you're posting entirely new objects - and will suffer from the same problem I ran into, when the declared property-type is of an abstract type. So you most likely won't be able to <em>edit</em> specific properties of concrete types on <em>existing</em> model objects, but only create new ones.</p> <p>So in other words, you will probably need to integrate this work-around into your binder to also be able to properly edit objects that were added to the view-model prior to binding... Personally, I feel that's a safer approach, since I control what concrete type gets added - so the controller/action can, indirectly, specify the concrete type that may be bound, by simply populating the property with an empty instance.</p> <p>I hope this is helpful to others...</p>
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    1. POPolymorphic model binding
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    1. USmindplay.dk
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    1. COThis worked for me very well. I worked for days to find a solution. I was able to create the new objects just as you describe, but the properties of the concrete type were never getting populated with the binder. Now they are.
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    2. COI'm glad this worked for someone - it seems most people don't understand these issue well enough to even care ;-)
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