How do I make the ModelBinder return null for a parameter?
===

I've got a POCO that I'm using as an argument to an action in MVC3.  Something like this:

My Type
----------

    public class SearchData
    {
        public string Property1 { get; set; }
        public string Property2 { get; set; }
        public string Property3 { get; set; }
    }

My Action
--------

    public ActionResult Index(SearchData query)
    {
        // I'd like to be able to do this
        if (query == null)
        {
            // do something
        }
    }

Currently, `query` is passed as an instance of `SearchData` with all of the properties as `null`.  I'd prefer that i get a `null` for `query` so I can just do the null check that I have in the above code.

I could always look at `ModelBinder.Any()` or just the various keys in `ModelBinder` to see if it got any of the properties for `query`, but I don't want to have to use reflection to loop over the properties of `query`.  Also, I can only use the `ModelBinder.Any()` check if query is my only parameter.  As soon as I add additional parameters, that functionality breaks.

With the current model binding functionality in MVC3, is it possible to get the behavior of returning null for POCO argument to an action?