Question

I have a json array containing integers and objects.

[1,2,3,{Name:"russia",Value:6},{Name:"usa",Value:"8"}]

I also have the following server-side class

class country {
  string Name;
  int Value;
}

How should I go about binding the json array to a server-side parameter ? I tried using a List<object> on server. It binds the integers fine but no country instances are created. Instead, primitive objects are created and added to the list.

Thanks.

Answer 1

Okay, I solved it at last. I created a custom model binder derived from the default model binder to accomplish this. Here’s the code.

public ActionResult Home(NonHomogeneousList input)

[ModelBinder(typeof(CustomModelBinder))]
class NonHomogeneousList : List<object>

public class CustomModelBinder : DefaultModelBinder
{
    public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
        {
            NonHomogeneousList model = (NonHomogeneousList)base.BindModel(controllerContext, bindingContext);
            if (model.Members != null)
            {
                IModelBinder countryBinder = Binders.GetBinder(typeof(Country));

            // find out if the value provider has the required prefix
            bool hasPrefix = bindingContext.ValueProvider.ContainsPrefix(bindingContext.ModelName);
            string prefix = (hasPrefix) ? bindingContext.ModelName + "." : "";

            for (var i = 0; i < model.Count; i++)
            {
                var member = model.Members[i];
                if (member.GetType().Equals(typeof(object)))
                {
                    var subKey =  CreateSubIndexName( prefix , i);
                    ModelBindingContext innerContext = new ModelBindingContext()
                    {
                        ModelMetadata = ModelMetadataProviders.Current.GetMetadataForType(null, typeof(Country)),
                        ModelName = subKey,
                        ModelState = bindingContext.ModelState,
                        PropertyFilter = bindingContext.PropertyFilter,
                        ValueProvider = bindingContext.ValueProvider,
                    };
                    var country = countryBinder.BindModel(controllerContext, innerContext);
                    model.Members[i] =  country;
                }
            }
        }
        return model;
    }
}
}