Question

Consider the following.

Models

public class DemographicsModel
{
    public List<QuestionModel> Questions { get; set; }
}

//Does not work at all if this class is abstract.
public /*abstract*/ class QuestionModel
{
    //...
}

public class ChooseOneQuestionModel : QuestionModel
{
    //...
}

public class ChooseManyQuestionModel : QuestionModel
{
    //...
}

public class RichTextQuestionModel : QuestionModel
{
    //...
}

public class TextQuestionModel : QuestionModel
{
    //...
}

Controller

[HttpPost]
public ActionResult Demographics(DemographicsModel model)
{
    //...
}

My view would have a DemographicsModel with numerous question of all the varying types as shown above. After the form is completed and POSTed back to the server, the Questions property of the Demographics model is re-populated with the correct number of questions but they are all of type QuestionModel instead of the concrete type.

How do I make this thing understand what type to instantiate?

Answer 1

Frazell’s answer would have worked if my root model was the one that was abstract. However, that’s not the case for me so what ended up working was this: http://mvccontrib.codeplex.com/wikipage?title=DerivedTypeModelBinder&referringTitle=Documentation