Question

It is my understanding that the default model binder is capable of turning

<input type="text" name="myType.property1" value="John Doe" />
<input type="text" name="myType.property2" value="22" />

into:

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult SomeAction(MyType myType)
{
     // This will be "John Doe"
     String someName = myType.property1;
     // This will be 22
     Int32 someNumber = myType.property2;


     // 
     // irrelevant magic
}         

In what scenario would I use the non-default model binder? I can’t think of a reason not to name the HTML input’s any differently than class property names. Please clarify, with an example.

Thank you!

Answer 1

In the scenario that your MyType for instance doesn’t have a default constructor (the default modelbinder needs a default constructor).
This can happen if you use the factory method pattern for creating a new object (very simple example just for illustration ;-):

public class MyType
{
    private MyType() // prevent direct creation through default constructor
    {  
    }

    public static MyType CreateNewMyType()
    {
        return new MyType();
    }
}

Then you would have to implement a custom modelbinder which calls the factory method CreateNewMyType() instead of creating a new MyType through reflection:

public class MyTypeBinder : DefaultModelBinder
{
    protected override object CreateModel(ControllerContext controllerContext,
                                          ModelBindingContext bindingContext,
                                          Type modelType)
    {
        return MyType.CreateNewMyType();
    }
}

Also if you’re not happy with the current functionality or implementation of the default modelbinder, then you can easily replace it with your own implementation.