How do I invoke UpdateModel from within a Custom ModelBinder? (MVC)

Question

Hi,

I'm creating a few custom binders for complex types in my Model. My model is composed of objects that have their own separate binders. I want the base object to do its dirty work and then populate the complex object it encapsulates by passing off to the standard ModelBinder routing. How do I do this?

For illustration purposes I've created a very simple example.

Say my model contains these objects.

public class Person
{
    public string Name {get; set;}
    public PhoneNumber PhoneNumber {get; set;}
}

public class PhoneNumber
{
    public string AreaCode {get; set;}
    public string LocalNumber {get; set;}
}

And I have the following Binders for each of these models. Not that the PersonBinder needs to populate the PhoneNumber but doesn't want to duplicate the code in the PhoneNumber binder. How does it delegate to back to the stardard Binder routing?

public class PersonBinder: IModelBinder
{
    public object BindModel(ControllerContext controllerContext, ModelBindingContext     bindingContext)
    {
        Person person = new Person();
        person.Name = bindingContext.ValueProvider.GetValue(String.Format("{0}.{1}", bindingContext.ModelName, "Name")).AttemptedValue

        // This is where I'd like to have the PhoneNumber object use binding from another customer ModelBinder.
        // Of course the bindingContext.ModelName should be updated to its current value + "PhoneNumber"
        person.PhoneNumber = ???;  // I don't want to explicitly call the PhoneNumberBinder it should go through standard Binding routing.  (ie.  ModelBinders.Binders[typeof(PhoneNumber)] = new PhoneNumberBinder();)

        return person;       
    }
}

public class PhoneNumberBinder: IModelBinder
{
    public object BindModel(ControllerContext controllerContext, ModelBindingContext     bindingContext)
    {
        PhoneNumber phoneNumber = new PhoneNumber();
        phoneNumber.AreaCode = bindingContext.ValueProvider.GetValue(String.Format("{0}.{1}", bindingContext.ModelName, "AreaCode")).AttemptedValue
        phoneNumber.LocalNumber = bindingContext.ValueProvider.GetValue(String.Format("{0}.{1}", bindingContext.ModelName, "LocalNumber")).AttemptedValue

        return phoneNumber;
    }
}

And of course I've registered my ModelBinders in the Global.asax.cs file.

protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();

    RegisterRoutes(RouteTable.Routes);

    ModelBinders.Binders[typeof(Person)] = new PersonBinder();
    ModelBinders.Binders[typeof(PhoneNumber)] = new PhoneNumberBinder();
}

Thanks,

Justin

Answer 1

Rather than write a binder you could user AutoMapper and handle the complex model construction in the Action.

Answer 2

Well I managed to come up with a solution. Please feel free to comment on its validity.

public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
     Person person = new Person();
     person.Name = bindingContext.ValueProvider.GetValue("Name").AttemptedValue

     if (bindingContext.ModelName == String.Empty)
     {
         bindingContext.ModelName = "PhoneNumber";
     }
     else
     {
         bindingContext.ModelName = bindingContext.ModelName + ".PhoneNumber";
     }

     PhoneNumber phoneNumber = new PhoneNumber();
     bindingContext.ModelMetadata = ModelMetadataProviders.Current.GetMetadataForType(() => phoneNumber, phoneNumber.GetType());

     IModelBinder binder = ModelBinders.Binders[typeof(PhoneNumber)];
     if (binder == null)
     {
          binder = ModelBinders.Binders.DefaultBinder;
     }

     person.PhoneNumber = binder.BindModel(controllerContext, bindingContext) as PhoneNumber;

     return person;                         
}

Here is a summary of what I've done.

1. Lookup the ModelBinder using the globally accessible ModelBinders.Binders collection (fallback to the default if one isn't registered)
2. Create the ModelMetadataProvider for the model I'm binding to.
3. Set the ModelName property of the bindingContext to the model property I'm trying to populate ("PhoneNumber").